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SIM lock
View on WikipediaA SIM lock, simlock, network lock, carrier lock or (master) subsidy lock is a technical restriction built into GSM and CDMA[1] mobile phones by mobile phone manufacturers for use by service providers to restrict the use of these phones to specific countries and/or networks. This is in contrast to a phone (retrospectively called SIM-free or unlocked) that does not impose any SIM restrictions.
Generally phones can be locked to accept only SIM cards with certain International Mobile Subscriber Identities (IMSIs); IMSIs may be restricted by:
- Mobile country code (MCC; e.g., will only work with SIM issued in one country)
- Mobile network code (MNC; e.g., AT&T Mobility, T-Mobile, Vodafone, Bell Mobility etc.)
- Mobile subscriber identification number (MSIN; i.e., only one SIM can be used with the phone)
Additionally, some phones, especially Nokia phones, are locked by group IDs (GIDs), restricting them to a single Mobile virtual network operator (MVNO) of a certain operator.
Most mobile phones can be unlocked to work with any GSM network provider, but the phone may still display the original branding and may not support features of the new carrier. Besides the locking, phones may also have firmware installed on them which is specific to the network provider. For example, a Vodafone or Telstra branded phone in Australia will display the relevant logo and may only support features provided by that network (e.g. Vodafone Live!). This firmware is installed by the service provider and is separate from the locking mechanism. Most phones can be unbranded by reflashing a different firmware version, a procedure recommended for advanced users only. The reason many network providers SIM lock their phones is that they offer phones at a discount to customers in exchange for a contract to pay for the use of the network for a specified time period, usually between one and three years. This business model allows the company to recoup the cost of the phone over the life of the contract. Such discounts are worth up to several hundred US dollars. If the phones were not locked, users might sign a contract with one company, get the discounted phone, then stop paying the monthly bill (thus breaking the contract) and start using the phone on another network or even sell the phone for a profit.[2] SIM locking curbs this by prohibiting change of network (using a new SIM).
In some countries, SIM locking is very common if subsidized phones are sold with prepaid contracts. It is important to note, however, that the technology associated with the phone must be compatible with the technology being used by the network carrier. A GSM cell phone will only work with a GSM carrier and will not work on a CDMA network provider. Likewise, a CDMA cell phone will only work with a CDMA carrier and will not work on a GSM network provider.[3][4] Note that newer (2013+) high end mobile phones are capable of supporting both CDMA and GSM technologies, allowing customers to use their mobile devices on any network. Examples of these mobile devices are the Apple iPhone 5c, 6 and newer, Motorola's G4, G5, X Pure, Samsung's Galaxy S6, S7, S8 smart phones, mostly phones based on a Qualcomm Snapdragon chipset or radio.
In some jurisdictions, such as Canada,[5] Chile,[6] China, Israel,[7] and Singapore[8] it is illegal for providers to sell SIM locked devices. In other countries, carriers may not be required to unlock devices or may require the consumer to pay a fee for unlocking.
Unlocking the phone, however, is almost universally legal.[9] Additionally, it is often legal for carriers to force SIM locks for certain amounts of time, varying by region.
Unlocking technology
[edit]A handset can be unlocked by entering a code provided by the network operator. Alternative mechanisms include software running on the handset or a computer attached to the handset, hardware devices that connect to the handset or over-the-air by the carrier. Usually the unlock process is permanent. The code required to remove all locks from a phone is referred to as the master code, network code key, or multilock code. If the phone is network locked it will typically display one of the following messages: SIM network PIN blocked, Enter lock PIN.
There can also be multiple levels of locks placed on the phone by networks, which block the use of other networks' SIM cards. These are usually referred to as "Network Control Key" (NCK) and "Service Provider Control Key" (SPCK), additionally, a Regional lock exists which is specific to Europe and it is called "Region Control Key" (RGCK).
Typically, a locked handset will display a message if a restricted SIM is used, requesting the unlock code. On recent phone models running Android software, the phone will display a message saying "SIM network unlock PIN" or "Enter Network Lock Control Key" if network locked. Windows phones will display the message, "This SIM card can only be used on specific networks. Contact your customer service center for the unlock code". Other handsets may display different messages such as "Enter special code" or "Enter unlocking code," or in some cases the handset will simply display a message stating that it is locked. Once a valid code is entered, the handset will display "Network unlocked" or "Network unlock successful".
The unlock code is verified by the handset and is generated by the manufacturer, typically by an algorithm such as a one way hash or trapdoor function. Sometimes big telecom providers change the original factory unlock codes as an extra layer of security against unlocking services. For various big brands such as Samsung and Motorola there is no algorithm but just a random code generator where the unlock codes are programmed in the phone itself and then saved in a big database managed by the manufacturer. For the other brands where the unlock codes are still based on algorithms those are based on the IMEI number and the MCC code and have been reverse-engineered, stolen or leaked. Some handsets can be unlocked using software that generates an unlock code from an IMEI number and country and operator details using the algorithm specific to the handset. Other manufacturers have taken a more cautious approach, and embed a random number in the handset's firmware that is retained by the manufacturer and the network on whose behalf the lock was applied. These handsets can still be unlocked by online services that have access to either inside people with the manufacturer or with the telecom networks, or they need to be connected to the computer with a cable where specific software will bypass the security and SIM-unlock the phone. Sometimes this is done by advanced calculations to bypass the security the official way and other times using exploits or overwriting parts of the firmware where the lock status is kept, and often even recover a phone that is bricked or completely damaged in the software sense.
Most handsets have security measures built into their firmware that protects them from repeated attempts to guess the unlock code. After entering more than a certain number of incorrect codes the phone becomes frozen. This is a state where the phone will display a security message that the phone needs a service. Older phones could no longer be used at all at this point, however modern smartphones often keep working with the original SIM but require extra work to then unlock them correctly. In extreme situations physical access to internal hardware via in-circuit debugging may be utilised (for example, via JTAG headers on a circuit board). Such access may be required to modify initialization software used for booting.
Hardlocked phones
[edit]A hardlocked phone is one in which a telecom provider has modified the firmware on the phone to make it impossible to manually enter the unlock codes in any way.
Economics
[edit]Handset manufacturers have economic incentives both to strengthen SIM lock security (which placates network providers and enables exclusivity deals) and to weaken it (broadening a handset's appeal to customers who are not interested in the service provider that offers it). Also, making it too difficult to unlock a handset might make it less appealing to network service providers who have a legal obligation to provide unlock codes for certain handsets or in certain countries.
In some cases, a SIM-locked handset is sold at a substantially lower price than an unlocked one, because the service provider expects income through its service. SIM locks are employed on cheaper (pay-as-you-go) handsets, while discounts on more expensive handsets require a subscription that provides guaranteed income. Unlocked handsets have a higher market value, even more so if they are debranded. Debranding involves reflashing or replacing the firmware to remove the operator logo or any limitations or customizations that have been imposed on the handset by the operator, and is usually accomplished with software designed for a particular handset model, however, most smart-phones can be debranded and unlocked solely with the use of special software.
The main reason to unlock a handset is to be able to use it with a different SIM card. Consumers may wish to continue using their previous provider with a new handset or when traveling abroad they may wish to connect to a foreign network with a prepaid subscription.
Nevertheless, the fundamental principle of GSM and its successors, is open interfaces which encourage competition among multiple vendors. This is the reason a mobile phone is, in fact, a combination of a phone and the subscriber identity module (SIM). Locking the phone to a network is not much different from having the SIM built into the mobile phone. Network operators in many industrialized countries are not bound by law to give the phone unlocking code to subscribers even after the expiry of the contract period.
Box breaking
[edit]A practice known as box breaking is common[10] in the United Kingdom and other markets. This involves purchasing subsidized handsets (usually pay-as-you-go) from retail stores, unlocking the phones, and then selling them (often abroad) for a higher price than the subsidised retail price. The SIM card that came with the handset is then either thrown away, sold, or used elsewhere. This practice is legal in the UK and provides a de facto limit to the extent to which networks are willing to subsidize pay-as-you-go handsets. While the act of box breaking is legal, some businesses are also engaging in illegal activities such as exporting the box-broken phones to other countries, to sell as grey market goods without paying import duties (known as carousel fraud) or substituting counterfeit batteries and chargers.[11][12]
Unlocking services
[edit]Some companies offer an online unlocking service. This service requires that individuals who wish to unlock a handset provide their IMEI number and sometimes also country and operator details to the company, either via email or a website. The company will then provide the unlock code for the handset. For some brands such as Nokia and Samsung various services also offer special remote-unlocking software with instructions, where a cable is needed to remove the SIM lock at home. Such companies may email the unlocking code or software which will remotely unlock the device. Some companies also offer unlocking services that require sending the handset's IMEI number. Other companies sell unlocking hardware, including devices which fit between the SIM card and the phone to spoof the original network identifier during registration and devices to read and edit the handset's firmware. The pricing for unlocking a device will vary depending on the network it is locked to and the handset model itself, as each unlock code is unique to each individual handset.
Unlock code generators
[edit]There are online services that will provide an IMEI unlocking service for DCT4 and DCT3 Nokia mobile phones.[citation needed] This method of unlock requires the user to know which carrier the mobile phone is locked to, and also needs to provide an IMEI. Generally, older model Nokia unlock codes are free and instantly retrievable by these services. The unlock codes retrieved must be entered into the mobile phone using the keypad.
For DCT4 and DCT3 Nokia, unlock codes consist of a "#" key, followed by "pw+", 10 (DCT3) or 15 (DCT4) digits, "+", and another number ranging from 1-7, and finally ends with a "#". Depending on the carrier which the phone is locked to, only some codes will work with the mobile phone. Most phones respond to the unlock codes ending in +1# or +7#, however some phones are configured to allow only one of the seven codes to work. The following is an example of a DCT4/DCT3 unlock code:
# pw+931882753035021+7#
DCT4 and DCT3 Nokia will only allow a maximum of five unlock attempts using the unlock code method. After five incorrect codes have been inputted, the phone will not allow the user to try any more codes (even if it is correct) and will require the owner to try other unlock methods.
Laws and practices
[edit]This section needs additional citations for verification. (August 2023) |
Many countries listed below have some form of SIM-locking laws specifying the period of SIM locking and the cost of obtaining unlocking codes.
Andorra
[edit]In Andorra, the state-owned communications mobile company Mobiland does not sell SIM-locked phones. As there is no competition, consumers usually buy standard mobile phones that are not locked to any specific carrier.[citation needed]
Austria
[edit]In Austria, unlocking is allowed at any time by the owner of the device. A lawsuit was decided in favor of a mobile operator who encouraged the unlocking of phones by providing links to free/cheap unlocking services.[13]
T-Mobile Austria charges 150 euros to unlock the iPhone for prepaid subscribers and in contract subscribers. For subscribers who have finished their 2-year iPhone contract, T-Mobile Austria charges 50 euros to unlock the iPhone.[14]
Australia
[edit]In Australia, carriers can choose whether to SIM/Network Lock handsets or not, however in practice, is rarely performed except in limited cases. Almost all handsets available on the Australian market have no such restriction.[citation needed]
One law professor, Dale Clapperton, gave a talk stating that bundling iPhone and mobile phone service could be violating the Trade Practices Act.[15] However, no other legal professional or academic has come out in support of this viewpoint.[16] This also doesn't address SIM locking per se, only as applied to subsidised iPhone purchases, and persistence of the lock beyond the contractual period.[citation needed]
Belgium
[edit]Until 2007, Belgium had laws prohibiting bundling, but they were challenged as violating European Directive 2005/29/EC The Unfair Commercial Practices Directive. On April 23, 2009, the European Court of Justice ruled against Belgium and struck down Belgium's anti-bundling law.[17] The Belgian government was given until May 2009 to change the law, failing which the European Commission would commence proceedings against Belgium. [citation needed] This leaves Canada, China, Singapore, and Israel as the only countries in the world that forbid SIM locking and contract/phone bundling outright.[18][5] Chile initiated a ban as of January 1, 2012.
Brazil
[edit]In Brazil, SIM locks are not prohibited. However, the mobile carrier must inform the consumer of the existence of a SIM lock. Anatel, Brazil's telecom regulator, requires the carrier to unlock free of charge the mobile phone if required by the user. After this regulation most telecom operators started voluntarily unlocking the devices as soon as it was purchased so one could leave the store with an unlocked phone.[19]
Canada
[edit]Under revisions to the Canadian Radio-television and Telecommunications Commission (CRTC) Wireless Code of Conduct effective 1 December 2017, all new devices must be sold unlocked, and carriers must offer to unlock phones purchased prior to this date free of charge.[5] Fees may be required if the customer was not under a contract or prepaid plan with the carrier.[20]
After the implementation of this rule, Bell Canada initially refused to offer unlocks for users who were not customers of the carrier (in contrast to Rogers and Telus Communications), but reversed course in February 2018 due to public backlash.[21][22] In a filing to the CRTC in August 2018, Bell also stated that it had begun to reimplement SIM locks on unsold phones as an anti-theft and safety measure (the phones are unlocked during the activation process when sold to a customer), citing increases in theft from store stocks since the implementation of the prohibition.[23]
Under the original version of the Wireless Code implemented 2013, carriers were required to offer unlocks no later than 90 calendar days from the start of a contract for subsidized devices, or immediately upon purchase of an unsubsidized device. The Code, however, did not expressly prohibit carriers from charging an unlock fee.[5][24]
Prior to the introduction of the Wireless Code, New Democratic Party MP Bruce Hyer first attempted to mandate SIM unlocking at the end of cell phone contracts when he introduced a private member's bill entitled the Cell Phone Freedom Act in 2010. The act would not have banned SIM locking but would have required wireless carriers to unlock phones at no charge at the end of a cell phone contract. The bill was introduced in two sessions of parliament but failed to pass either time.[citation needed]
China
[edit]Under a regulation enacted by the Ministry of Industry and Information Technology, locking phones to a specific carrier is prohibited if other carriers are also using the same type of network technology. Therefore, all phones approved to be sold in China are never locked to begin with regardless of whether the consumer purchased the phone under a contract or not. However, since all three Chinese carriers each uses a different network technology after the adoption of 3G, carriers started to ask phone manufacturers to disable support for network technologies not used by such carrier even if the phone has been originally designed to be capable of supporting those network technologies. Such a move does not result in violation of the ban on phone locking. For example, an iPhone 6 was designed to be capable of supporting LTE FDD, LTE TD, CDMA, and WCDMA technologies but China Mobile reached a deal with Apple to create a special model for China Mobile in addition to the off-contract retail model sold by Apple and third party vendors with the capability to support LTE FDD, CDMA, WCDMA, which are the technologies not used by China Mobile, disabled, effectively making such special contract model incompatible with the 3G and 4G networks of other carriers even though such phones are never locked.[citation needed]
Colombia
[edit]Starting October 1, 2011, all the mobile telephone services providers, must sell to all users unlocked devices and provide free of charge support to unlock previously sold devices. This regulation was ordered to enable mobile number portability and to facilitate the reduction on costs ordered simultaneously.[25]
Chile
[edit]Since 1 January 2012, newly sold phones must be unlocked. Previously bought locked phones had to be unlocked for free. The regulation was put in place in order to implement mobile number portability.[6] However, the law only requires phones to be usable with all Chilean providers. It does not cover international unlocking for use outside Chile, so users may have to pay for the unlocking service.[citation needed]
A new related issue is present since 23 September 2017, every IMEI have to be registered so the phone works in the country. For local carriers, they do the process, but to use a phone from outside the country, each user has to register it. IMEI Registration.[26]
Croatia
[edit]In Croatia, for devices bought on contract, the mobile operator must provide the unlock code on the user's request free of charge. Such request can be made immediately after buying the phone, and the operator has a 15-day period to fulfill the request. For devices bought on a prepaid plan, the user has to wait at least 12 months before submitting such request.[27]
Denmark
[edit]The carrier can choose to bind contracts up to 6 months from the contract's start. Many of the carriers choose not to lock the phones. Only Hi3G ("3") lock their phones, but can only do so for six months.[28] If the phone needs to be unlocked within the first six months, the carrier can charge DKK 500 (~ €67)[28] for the unlock. After six months, the carrier is obliged by law to unlock the phone free of charge. But the consumer needs to contact the original supplier, and provide the IMEI and original phone number for which the phone was sold.[citation needed]
Ecuador
[edit]Although there is no specific law preventing SIM locking, as of December 2009 Ecuador's two biggest carriers, Porta and Movistar, unlock phones previously sold by them, without charge.[29]
European Union
[edit]Countries in the European Union (EU) each have their own legislation on SIM locking, but must comply with the EU Unfair Commercial Practices Directive (Directive 2005/29/EC of 2005). As noted above, this directive has been successfully applied in Belgium to overturn that country's previous ban on bundling phones with contracts. However, carriers in many countries in the EU do not necessarily associate a phone's SIM lock status to the customer's tie-in contract status.
Finland
[edit]In Finland, carriers are not allowed to sell SIM-locked GSM phones, nor are they allowed to offer tie-in sales on GSM equipment. Under Finnish law, a tie-in sale is defined as selling the equipment for a discounted price contingent on the consumer also acquiring a new service contract from the seller. Under the terms of a provisional exception, valid from 2006 until 2009, tie-in sales were permitted with 3G handsets, and 3G equipment which is purchased under such tie-in sales may be SIM-locked. The SIM lock must be removed free of charge at the conclusion of the tie-in contract, within a maximum duration of 2 years.[30] In 2008, the Finnish government was preparing to extend the exception, and at the same time, was considering reducing the duration of tie-in contracts to one year.[31]
France
[edit]In France, SIM locks are not prohibited. However, the mobile operator must inform the consumer of the existence of a SIM lock, and the subscriber has the right to request that the lock be removed at any time. No later than three months after the subscription of the contract, the mobile operator must "systematically and free of charge" provide the subscriber with a procedure to deactivate the SIM lock. Proposal to shorten the time that operators may charge a fee for removing the SIM lock prior from six-month to the three-month deadline.[32]
Germany
[edit]In Germany, there does not appear to be any effective law regulating SIM locking.[original research?] For example, the iPhone was initially offered for sale in Germany exclusively through T-Mobile, and it was locked to T-Mobile's network. They began to provide unlocking codes for that phone after they were sued by Vodafone and a temporary injunction was issued requiring T-Mobile to do so. Vodafone's injunction was later overturned, and the iPhone is again available exclusively locked to T-Mobile.[33] While T-Mobile Germany told the court that they would unlock the iPhone after the contract, they were doing it voluntarily.[citation needed]
While SIM locking is legal, a court ruled in 2012 that providers must clearly inform potential customers about the SIM lock.[34]
As of 2015, usually only prepaid mobile phones are sold with a SIM lock. Phones sold with a contract stipulating monthly payments are not typically locked (as the monthly payments are due no matter what network the phone is used on). Also, most providers will unlock the phone on demand. Usually a fee is charged during the first two years after purchase; afterwards the unlocking is free. As of 2022, new phones are rarely distributed with a SIM lock;[35] old phones however may still be locked.
Honduras
[edit]In Honduras, there is a general law applicable to all consumer relations engaged in the national territory and provided by natural or legal persons, public or private. This law is called "Ley de Proteccion al Consumidor"[36] or "Consumer Protection Act of Honduras", approved by Legislative Decree No.24-2008, and it regulates the activities of any goods and services providers stating the principles that they must follow in order to operate in this country.
Article 20 of this law states the prohibitions that sellers are obliged to abide when selling a good or providing a service to people. Paragraph 7 of this article states that it is prohibited to a provider to "place seals, adhesives, duct tapes or analogous mechanisms, which prevent the consumer to make free use of the product, except those mechanisms used by the manufacturer for warranty purposes".
Even though the existence of this law, local carriers continue to apply SIM restrictions to the phones they sell. For example, the iPhone is sold by Claro in Honduras and is SIM-locked.[37] which suggests that this general consumer protection law does not prohibit SIM locking of cell phones[38]
Hong Kong
[edit]In Hong Kong, carriers are not allowed to SIM-lock a phone for the sole purpose of tying customers to their network. But Hong Kong carriers can SIM-lock a phone to protect the handset subsidy, to enforce mobile plan contracts or to protect from theft.[39] After the initial purchase subsidy has been recovered, or the full cost of the equipment has been paid up under a rental or installment agreement, the carrier must provide a detailed procedure for unlocking the equipment free of charge upon request.[citation needed]
India
[edit]SIM locking is not common in India. Initially, each state in India had a different mobile network operator and roaming across states was prohibitive. It was cheaper to change the SIM card than pay high roaming charges. The number of inter-state travelers demanded unlocked phones. Usually, phones and SIM cards are sold separately. Mobile phone manufacturers sell phones directly to customers rather than through network operators. Dual SIM phones are quite common in use, with users choosing to make calls using a cheaper operator suitable for the particular call and time of the day from a Dual SIM phone without even switching it off. This along with other factors, encouraged competition among network operators and brought down the mobile phone call charges in from the initial ₹32 (US$0.75) in 1996 to ₹0.50 (US$0.005 approx.) in 2011. The rates still differ from one service provider to another and across different tariff schemes provided by the same operator. Telecom Regulatory Authority of India (TRAI) is the independent regulator of the telecommunications business in India,[40] established to check call rates and resolve all communication related issues and holds the upper hand in fixing call rates.
Israel
[edit]According to the Arrangements Law passed on December 29, 2010, Israeli carriers are banned from locking handsets sold by them, and are obligated to unlock any handset previously sold at no charge.[7]
Italy
[edit]Italy has SIM locking laws requiring that carriers must specify the amount of subsidies, and allow subscribers to obtain unlocking codes after nine months by paying half of the listed subsidies. After 18 months, the SIM lock must be removed.[41]
Japan
[edit]Japan's Ministry of Internal Affairs and Communications has legislated that all smartphones and tablets released after May 1, 2015, by NTT DoCoMo, au/Okinawa Cellular and SoftBank Mobile (the three major carriers in Japan) must be sold without a SIM lock upon request from customers and without any cost to the customer involved. Before that, from 2011 until 2015, only NTT DoCoMo and au/Okinawa Cellular would remove the SIM lock from phones with a SIM unlock function after the phone is kept or used at least six months after purchase.[42]
Monaco
[edit]In Monaco, the partially state-owned communications mobile company Monaco Telecom does not sell SIM-locked phones. As there is no competition, consumers usually buy standard mobile phones that are not locked to any specific carrier.
Netherlands
[edit]Dutch mobile carriers have an agreement[43] with the Netherlands' telecom regulator, OPTA, to establish a code of conduct[44] with respect to SIM locking — specifically, unlocking fees can be charged within the first 12 months and SIM lock cannot last longer than 12 months.[45]
In a 2002 letter to the Dutch Secretary of State of Economic Affairs, OPTA stated that the telecom regulator has decided to start working on the formalization of the voluntary code of conduct into legislation.[46] However, a 2006 report written by the Dutch Ministry of Economic Affairs,[47] stated that competition in the Dutch mobile market is sufficient and the formalization of the voluntary code of conduct into legislation is not needed. Thus there are no SIM locking laws in the Netherlands.[48]
New Zealand
[edit]Locking was planned in New Zealand before May 2008[49] when Vodafone New Zealand announced they would begin locking handsets. The company had planned to charge $50 to unlock them, but then relented. It is speculated that the intention to lock was prompted by Telecom New Zealand building their new mobile network based on UMTS technology, allowing handsets to change networks for the first time. Until that point in time, Telecom's network (the only other mobile network at that time) was based on CDMA technology, meaning that it was not possible to change networks. 2degrees were also building a mobile network based on UMTS at this time. After pressure from the Commerce Commission, Vodafone relented on its locking policy, and will unlock any locked phones for free once they have been owned for nine months. You can pay to have it unlocked prior to this.[50][51]
Following speculation of a new lower cost, MNVO of Telecom XT details were leaked regarding the Skinny Mobile Network, which would SIM lock handsets.
As of 2015, Vodafone, Spark, Skinny, and 2Degrees all charged a $30 unlock fee for phones owned for less than 9 months. As of 2020, Spark charges a $30 unlock fee for phones owned for less than 9 months, unless the customer is on a Pay Monthly 24 Month Plan. 2Degrees dropped its fees for unlocking phones.[52]
Norway
[edit]Phones sold with a subscription are usually SIM locked to Norwegian carriers. The fee varies depending on how long it has been since you purchased your mobile phone. After 12 months, you can enter the operator lock code yourself without paying for it.[citation needed]
Pakistan
[edit]Ufone has started SIM Locking with the release of its new smartphone named Smart U5 developed by Emitac Services, UAE. U5 comes SIM locked to Ufone only. No other SIM can be used on the U5.[citation needed]
Peru
[edit]According to OSIPTEL Peru's telecom regulator, article 23 of the Terms of use, mobile carriers can sell phones locked for a lower price for 12, 18 or 24-month contracts, but also must sell unlocked devices for the full price. The same article dictates the customer can request the unlock code for free after 12 months from the purchase date, no matter if the contract is still in place. The sole exception is if the customer cancels the contract before its end and pays the remaining cost, at which point the customer can request the device be unlocked at any time. OSIPTEL plans to reduce the time customers must wait to remove their SIM locks to 6 months.
Portugal
[edit]A 2006 study sponsored by the Portugal regulator, ANACOM, on handset subsidies and SIM locking concluded that there are no special regulatory concerns on offering subsidized SIM-locked equipment in exchange for signing a contract tying a customer to a particular network. Network providers are allowed to apply SIM locks as they see fit, and they may voluntarily remove them if they choose to do so. In the paper, the author stated that the average unlocking fee charged by Portuguese carriers is 90-100 euros.[53] A recently approved law[54] requires network operators to unlock a device free of charge if the respective contract has already expired (But they refuse to do so charging at least 10 euros). It also establishes limits to the fees that operators may charge to unlock a device while it is still under contract.
Romania
[edit]Romanian telecom regulator ANCOM signed a code of conduct with several Romanian carriers providing that as of September 1, 2009 mobile operators selling handsets locked within their own network have to inform clients whether the handset is locked and provide unlocking upon request. It is "self-regulation" by the carriers to prevent the regulator from actually imposing regulations on them. If the handset is not purchased together with other electronic communications services, the mobile telephony operator that sells it will bear the unlocking costs and will not bind the terminal unlocking by the purchase of other services or by the payment of other fees.[citation needed]
If the handset is purchased as part of a promotional package or at a preferential price and the customer requires the unlocking before the expiry of the minimum period provided in the contract for communications services concluded with the operator, the customer will have to pay both the unlocking fee and the penalty for the anticipated unlocking of the handset. The price charged to unlock handsets will not exceed the costs of this operation and operators are obliged to meet unlocking requests within 15 days.[55]
Russia
[edit]SIM locking is not common in Russia, but they have huge potentials to sell unlocked phones. Most mobile phones sold in Russia doesn't have extensive bundlings, customizations as well as the carrier-specific bloatware. Beeline-branded phones are always locked to their network operator.[citation needed]
Serbia
[edit]In telecommunication contracts it is frequent the practice to lock the use of a sim card of one operator with a phone acquired through the same mobile operator. Obstructing the unlocking of the phone may be illegal if the consumer is entitled to it.[citation needed]
Singapore
[edit]In 1997, Singapore's then-telecommunications regulator, Telecommunication Authority of Singapore (now Infocomm Media Authority of Singapore) enforced a legislation where telcos (Singtel, StarHub, M1, Circles.Life, MyRepublic, TPG Telecom and Zero1) are not allowed to SIM-lock devices, such as phones, tablets and smartwatches that are imported and sold in Singapore.[56][57] In August 1997, TAS warned at least one operator, M1, for selling SIM-locked phones.[58]
Spain
[edit]In 1998, the then-Spanish telecom regulator, Tribunal de Defensa de la Competencia (now Comisión Nacional de los Mercados y la Competencia), saw that Spanish mobile carriers already provided unlocking codes voluntarily for a fee within the first 12 months and for free after 12 months, so it decided not to establish any legal framework in Spain.[59] CMT has not revisited this decision since then, therefore there are no SIM-locking laws in Spain.
Sweden
[edit]In Sweden, carriers are required to unlock handsets after 12 months since purchase. This applies both to on-contract and pay as you go phones. All carriers will charge a fee of 300 SEK (approximately $45) or 350 SEK (approximately $50), depending on carrier, to unlock the handset. However, as of 2016, most carriers have stopped locking phones altogether.[citation needed]
Switzerland
[edit]SIM locking may be particularly common in Switzerland. Swisscom began lifting SIM lock since July 2013. Sunrise prepaid mobile phones have a SIM lock for 2 years from purchase.[citation needed]
Thailand
[edit]This section needs to be updated. (January 2019) |
Thailand is also another country that forbids outright SIM locking and as a result, no phones are sold in the market are subsidized by carriers. Up until recently mobile phone manufacturers have their own store fronts and mobile carriers are only the service providers.[citation needed]
Turkey
[edit]SIM locking is forbidden by the regulatory authority in Turkey since 2013.[60][61] There are conflicting and varying reports about former practices of SIM locking by operators. A newspaper column from 1997 criticizes Telsim's SIM locking policy: "... you cannot quit Telsim until the phone becomes waste, the only way to quit Telsim is buying a new phone."[62] Turkcell's SIM locking policy has been subject to a lawsuit in 2001, resulting in Turkcell being fined.[63] BlackBerry phones sold by Turkcell and Vodafone were SIM locked, however, could be unlocked on request without any conditions.[64] Yet, the SIM locking practice was only confined to phones sold by operators and it is not clear if operators enforced SIM locking on the phones sold by them tightly or not and if the practice was widespread. Phones sold by other channels were strictly unlocked. Three major mobile network operators, Turkcell, Türk Telekom and Vodafone still offer phones with long term contracts, however these phones are sold unlocked.[citation needed]
United Kingdom
[edit]In the United Kingdom, mobile phone network providers are not obliged to provide unlocking, even after the end of the contract. Ofcom, UK's telecom regulator, allowed 3 to sell a mobile phone with the SIM card permanently superglued to the phone.[65] Most operators offer some form of unlocking service, depending on the state of the contract and the model of phone, but usually for a charge. The full Oftel 2002 SIM-lock position paper specifies that there is no SIM-locking law in the UK; the regulator wants only "consumer awareness". The examples within the position paper are just "examples" of current carrier practices for illustration purposes, but do not reflect any official Oftel regulation.[66] The main networks often agree to unlock handsets for a charge, either at the end of a contract or, for prepaid handsets, after several months. Some Blackberry handsets supplied by Vodafone (e.g., Storm)[67] are examples of a UK carrier not offering unlocking codes. As of April 2011 O2 will unlock any of their pay-monthly phones for free, even if they're still in contract, with the exception of handsets made exclusively for them, such as their Palm devices.[68] Carphone Warehouse, one of the largest UK phone retailers, offers unlocked phones with most PAYG deals.[citation needed] As of January 1, 2014, all phones sold by 3 UK are unlocked. Phones bought before this date will be unlocked for free.[69]
On 17 December 2019, Ofcom announced that it would explore a mandate banning SIM locking.[70] On 27 October 2020, The UK's mobile networks are to be forbidden from selling phones locked to their services from December 2021.[71]
United States
[edit]One of the two American GSM carriers, T-Mobile,[72] will unlock handsets for those with active account in good standing for at least 40 days and no unlock code request in the last 90 days. The other, AT&T Mobility, is required to do so upon request (with some exceptions and requirements) after ninety days of active service under the terms of a class action settlement.[73] Prior to the settlement, AT&T would[74] usually do so once one has concluded their contract, and in some other situations. AT&T had in the past stated that it would not unlock iPhones under any circumstances, regardless of the legality of doing so, even after customers are out of contract. However, AT&T has since announced that starting April 8, 2012, it will begin unlocking off-contract iPhones, provided that the customer's account is in good standing.[75] AT&T also has an unannounced policy of unlocking iPhones for United States service members who are deployed overseas –even if they are still under contract.[76]
Before carriers began voluntarily providing unlock codes for all phone models, in 2010 the Electronic Frontier Foundation (EFF) successfully convinced the United States Copyright Office to allow an exemption to the general prohibition on circumvention of copyright protection systems under the Digital Millennium Copyright Act of 1998 for unlocking of phones through user self-help (sometimes referred to as "hacking").[77] This exemption has become less important now that most carriers are voluntarily providing unlock codes.
According to a ruling effective October 28, 2012, it will be illegal to unlock phones purchased 90 days after this date or later without the carrier's permission.[78] In other words, users can already unlock phones they already own, and phones purchased before January 29, 2013, but phones purchased after this point can only be unlocked with the carrier's permission.
In March 2013, the Obama administration and the Federal Communications Commission said consumers should also be able to switch carriers and keep their actual phones.[79]
On August 1, 2014, President Obama signed into law the Unlocking Consumer Choice and Wireless Competition Act (S. 517; 113th Congress), a bill legalizing unlocking cellphones in the US.[80][81] The bill passed in the United States Senate on July 15, 2014, and in the United States House of Representatives on July 25, 2014.
Sprint agreed to allow domestic unlocking on all mobile devices launched after February 15, 2015.[82]
It is possible to buy unlocked phones in the U.S. Some online retailers sell phones that come unlocked from the manufacturer, that is, they were never locked in the first place.[citation needed]
See also
[edit]References
[edit]- ^ Price, Christopher (October 8, 2011). "In-Depth: Why iPhone 4S Can't use CDMA on GSM Networks". PhoneNews.com. Mobile Media Ventures. Archived from the original on September 21, 2021. Retrieved September 24, 2016.
CDMA ... us [es] an antiquated Master Subsidy Lock code system.
- ^ "What is a Locked Phone and Why do Carriers Lock Them?". 29 January 2014.
- ^ "10 Most Frequently Asked Questions Answered Pertaining the FCC Guidelines on Mobile Device Unlocking". 27 February 2015.
- ^ Ways to check the Network, product code and country of your Phone Guidelines to find about your network provider
- ^ a b c d "Telecom Regulatory Policy CRTC 2017-200". CRTC. 15 June 2017. Retrieved 15 June 2017.
- ^ a b "Empezó a regir desbloqueo de equipos celulares" (in Spanish). Subsecretario de Telecomunicaciones. 2 January 2012. Archived from the original on 2015-10-17. Retrieved 13 August 2015.
Normativa de SUBTEL establece que desde el 01 de enero de 2012, todos los equipos terminales que sean utilizados en las redes móviles, no deberán, desde el momento de su ofrecimiento al público bajo cualquier modalidad contractual, estar bloqueados o afectos a configuraciones técnicas que restrinjan su uso sólo a la red de una operadora.
- ^ a b "אושרו עוד שלוש מהפכות צרכניות בתחום הסלולר (hebrew)". TheMarker. Archived from the original on 2010-12-11. Retrieved 7 October 2014.
- ^ "TAS Fines M1 For Unauthorised Frequency Transmission And Issues Warning Over Sale Of SIM-Locked Cellular Phones" (Press release). Infocomm Development Authority of Singapore. 1997-09-08. Archived from the original on 2007-08-12.
- ^ "Is iPhone unlocking illegal?". SimonlymetInternet. Archived from the original on 31 October 2012. Retrieved 23 September 2012.
- ^ "Box breaking investigation exposes retail staff breaches". Mobile News Online. Archived from the original on 13 October 2014. Retrieved 7 October 2014.
- ^ "Fraud cases up, financial losses down". The Register. Retrieved 7 October 2014.
- ^ "HMRC Stings Missing Traders for GBP12 Million". www.tax-news.com. Archived from the original on 16 July 2011. Retrieved 13 January 2022.
- ^ „YESSS! gegen T-Mobile Klage erfolgreich“ Archived 2013-09-30 at the Wayback Machine, Telekompresse-Bericht über das Urteil zugunsten von YESSS!, 2005-06-29
- ^ "Entsperrung des iPhone". Faq.t-mobile.at. 2010-05-14. Retrieved 2013-06-21.
- ^ "Latest Reviews". February 25, 2008.
- ^ "TechRepublic - A Resource for IT Professionals". Builderau.com.au. Retrieved 2013-06-21.
- ^ "Belgium law was struck down". Retrieved 7 October 2014.[dead link]
- ^ "High iPhone Price Blamed on Subsidy Ban". The Washington Post. Retrieved 7 October 2014.
- ^ "Bloqueio" (in Portuguese). Anatel. Archived from the original on 16 September 2012. Retrieved 25 October 2012.
- ^ "Wireless Code – Request to clarify the device unlocking rules". CRTC. 2019-05-23. Retrieved 2019-06-05.
- ^ "Bell offers free phone unlocking for all following protests". CBC News. Retrieved 2018-08-13.
- ^ "'It's ridiculous': Critics blast Bell for not unlocking all phones for free under new CRTC rules". CBC News. Retrieved 2018-08-13.
- ^ "Bell returns to stocking carrier-locked phones at retail locations". MobileSyrup. 2018-08-13. Retrieved 2018-08-13.
- ^ "Canadians can cancel their wireless contracts after two years under new CRTC wireless code". CRTC. Retrieved 2013-06-03.
- ^ "Desde el 1 de octubre los colombianos podrán comprar los celulares con las bandas abiertas, una medida del gobierno que fortalece los derechos de los usuarios de telecomunicaciones en el país". Mintic.gov.co. Retrieved 2013-06-21.
- ^ "Homologación y registro multibanda" (in Spanish). Subsecretario de Telecomunicaciones. 23 September 2017. Retrieved 13 August 2015.
A partir del 23 de septiembre entra en vigencia la nueva normativa multibanda SAE la cual exige que se registre tu IMEI o número único de identificación celular en las redes locales Chilenas.
- ^ "Pravilnik o načinu i uvjetima obavljanja djelatnosti elektroničkih komunikacijskih mreža i usluga (izmjene od NN 24/15)" (PDF). HAKOM. Retrieved 2015-10-10.
- ^ a b "Teleselskaber dropper simlås". 20 May 2010.
- ^ "Claro - Ecuador". Porta.net. Archived from the original on 2011-03-03. Retrieved 2013-06-21.
- ^ "Communications Market Act" (PDF). finlex.fi. Archived from the original (PDF) on December 9, 2008. Retrieved 22 March 2018.
- ^ "Newsroom - thisisFINLAND". finland.fi. Retrieved 22 March 2018.[dead link]
- ^ "Proposition de loi relative aux télécommunications". Senat.fr. Retrieved 2013-06-21.
- ^ "Deutsche Telekom Wins Ruling in IPhone Sales Dispute (Update3)". Bloomberg. December 4, 2007.
- ^ Dr. Cornelius Renner. "Nicht ohne SIM-Lock-Hinweis". medienrecht-blog.com (in German). Archived from the original on 5 January 2016. Retrieved 23 October 2015.
Wie die Wettbewerbszentrale mitteilt, hat das Landgericht Bonn mit Beschluss vom 1. Oktober 2012 – 11 O 39/12 – die Werbung der Telekom ohne (rechtzeitigen) Hinweis auf das SIM-Lock und das Netlock des Telefons als irreführend verboten.
- ^ Ebert, Marina. "SIMlock und Netlock: Das sind die Unterschiede". inside digital (in German). Retrieved 2022-11-29.
- ^ "Decreto No.24-2008 : El Congreso Nacional" (PDF). Sic.gob.hn. Archived from the original (PDF) on 2012-07-10. Retrieved 2013-08-24.
- ^ "iPhone: Wireless carrier support and features". Support.apple.com. 2013-06-17. Retrieved 2013-06-21.
- ^ "The Law Against Unlocking Cellphones Is Anti-Consumer, Anti-Business, and Anti-Common Sense". The Atlantic. September 2010. Retrieved 2020-02-02.
- ^ OFTA, Office of the Telecommunications Authority, Hong Kong
- ^ "TRAI website". Retrieved 2008-08-19.
- ^ "Consumer friendlier SIM-lock mechanism". Archived from the original on 2012-03-08. Retrieved 2016-02-07.
- ^ "Mobile phone service operators lift SIM locks". japantoday.com. Retrieved 22 March 2018.
- ^ "Dutch Ministry of Economic Affair paper stating OPTA agreement with Dutch mobile carriers". 14 October 2010. Retrieved 7 October 2014.
- ^ "Establishment of Conduct of Conduct". 14 October 2010. Retrieved 7 October 2014.
- ^ "OPTA website on sim-locking". opta.nl. Archived from the original on 20 July 2003. Retrieved 22 March 2018.
- ^ "OPTA letter to EZ". Archived from the original (PDF) on 2012-03-17. Retrieved 7 October 2014.
- ^ "EZ 2006 Report". 14 October 2010. Retrieved 7 October 2014.
- ^ "In the runup of the European launch of the iPhone, a Dutch Macintosh website asked a lawyer to provide a simple summary of the SIM-locking situation in the Netherlands". macwereld.nl. Archived from the original on 17 September 2013. Retrieved 22 March 2018.
- ^ Griffin, Peter (May 2, 2008). "Vodafone's mobile phone lock-down". The New Zealand Herald. Retrieved November 11, 2011.
- ^ "Unlock your mobile phone". www.vodafone.co.nz. Retrieved 22 March 2018.
- ^ "Vodafone relents on mobile lock". Stuff.co.nz. May 27, 2008. Retrieved November 11, 2011.
- ^ "Unlock your phone". 7 June 2015.
- ^ "Handset Subsidies – an Empirical Investigation" (PDF). anacom.pt. Retrieved 22 March 2018.
- ^ "ANACOM - Desbloqueamento de telemóveis - novas regras". Anacom.pt. 2010-07-13. Retrieved 2013-06-21.
- ^ "Operatorii de telefonie mobila vor debloca, la cerere, telefoanele codate in reteaua proprie" (in Romanian). Ancom. 29 September 2009. Archived from the original on 2016-01-05.
- ^ "Switch mobile operator without changing SIM cards? IMDA wants feedback on eSIM tech". Channel NewsAsia. Archived from the original on 2019-11-20. Retrieved 2018-06-06.
- ^ "Consultation Paper for eSIM" (PDF). Infocomm Media Development Authority. 2018-06-06. Retrieved 2018-06-06.
- ^ "TAS Fines M1 For Unauthorised Frequency Transmission And Issues Warning Over Sale Of SIM-Locked Cellular Phones" (Press release). Infocomm Media Development Authority of Singapore. 1997-09-08.
- ^ "Spanish telecom regulator decided not to legislate SIM locking in 1998" (PDF). cmt.es. Archived from the original (PDF) on 26 February 2012. Retrieved 22 March 2018.
- ^ "SIM kilit uygulaması kaldırıldı". Milliyet (in Turkish). 2013-06-19. Retrieved 2023-07-13.
- ^ "Bilgi Teknolojileri ve İletişim Kurumu SIM kilit uygulamasını kaldırdı". www.hurriyet.com.tr (in Turkish). 2013-06-19. Retrieved 2023-07-13.
- ^ "Tüketicinin Erkan abisi". www.hurriyet.com.tr (in Turkish). 1997-10-06. Retrieved 2023-07-13.
- ^ "Turkcell'e 7 trilyon lira ceza". arsiv.ntv.com.tr. Retrieved 2023-07-13.
- ^ "BLACKBERRY SIM KILIT KODU HAKKINDA HERŞEY". DonanımHaber Forum (in Turkish). 2010-07-13. Retrieved 2023-07-13.
- ^ "3 UK superglued SIM card into the cell phone". Archived from the original on 12 January 2015. Retrieved 7 October 2014.
- ^ "OFCOM Review of SIM-locking policy". Ofcom. Retrieved 7 October 2014.
- ^ "Vodafone UK's position on not offering unlocking codes to Blackberry Storm". Vodafone. Retrieved 7 October 2014.
- ^ "Unlocking your O2 device for use on a different network". O2. February 2015. Retrieved 2020-02-02.
- ^ "Unlocking a 3 device for use on another network". Archived from the original on 3 May 2017. Retrieved 15 April 2017.
- ^ "Ofcom proposes locked-handset ban". 2019-12-17. Retrieved 2019-12-17.
- ^ "Mobile networks banned from selling locked phones". 2020-10-27. Retrieved 2020-10-27.
- ^ "SIM Unlock your phone | Support". Support.t-mobile.com. Retrieved 2013-06-21.
- ^ Article title (Archived by WebCite® at https://web.archive.org/web/20111117091504/http://www.attlockinglawsuits.com/pdf/meolinot.pdf)
- ^ Pegoraro, Rob (2008-05-29). "It's Not The Money, Can You Hear Me?". The Washington Post. Retrieved 2010-05-23.
- ^ Golson, Jordan (April 6, 2012). "AT&T Will Unlock Off-Contract iPhones Starting Sunday, April 8". MacRumors.com. Retrieved April 11, 2012.
- ^ Golson, Jordan (April 9, 2012). "AT&T Unlocking In-Contract iPhones for Deployed Service Members". MacRumors.com. Retrieved April 11, 2012.
- ^ United States Copyright Office (July 27, 2010). "Federal Register / Vol. 75, No. 143 / Tuesday, July 27, 2010 / Rules and Regulations"" (PDF). Federal Register. Retrieved August 21, 2012.
- ^ United States Copyright Office (October 22, 2012). "Exemption to Prohibition on Circumvention of Copyright Protection Systems for Access Control Technologies" (PDF). Federal Register.
- ^ Wyatt, Edward (4 March 2013). "F.C.C. Urges a Right to Unlock Cellphones". The New York Times. Retrieved 22 March 2018.
- ^ Hattem, Julian (25 July 2014). "House votes to allow cellphone 'unlocking'". The Hill. Retrieved 25 July 2014.
- ^ "President signs cell phone unlocking bill into law". cnet. August 2, 2014.
- ^ "Legal / Regulatory & Consumer Resources".
SIM lock
View on GrokipediaA SIM lock, also referred to as a network lock or carrier lock, is a software-based restriction embedded in cellular telephones by mobile network operators to limit the device's functionality to SIM cards issued exclusively by that operator.[1][2] This mechanism verifies the SIM card's carrier-specific identifiers, such as the International Mobile Subscriber Identity (IMSI), and rejects incompatible cards, thereby enforcing network exclusivity.[3] Carriers implement SIM locks primarily to subsidize device costs through discounted pricing or installment plans, ensuring customers fulfill contract terms before gaining portability to rival networks.[4][5] While enabling aggressive pricing strategies that expanded mobile access, SIM locking has drawn scrutiny for curtailing consumer freedom to switch providers, potentially inflating costs and stifling competition in telecommunications markets.[6] Regulatory responses worldwide address these concerns, with practices varying by jurisdiction; for instance, certain countries like China and Singapore prohibit SIM locking entirely, while others impose unlocking mandates post-contract or after specified periods.[7] In the United States, the Federal Communications Commission stipulates that carriers must unlock devices upon request no later than one year after activation, subject to fulfillment of reasonable usage or payment conditions, amid ongoing proposals to reduce this timeline to 60 days to enhance consumer mobility.[8][9] Unlocking typically involves carrier-provided codes or third-party services, though unauthorized methods can void warranties or trigger legal issues in restrictive environments.[1]
Definition and Core Concepts
Mechanism and Functionality
The SIM lock, also known as a network or carrier lock, is a software restriction embedded in the firmware of compatible mobile phones, primarily those adhering to GSM standards, that limits operation to SIM cards issued by a specific carrier. Upon insertion of a SIM card, the phone's baseband processor reads the International Mobile Subscriber Identity (IMSI) stored on the SIM, which encodes the Mobile Country Code (MCC, typically the first three digits) and Mobile Network Code (MNC, the following two or three digits) to uniquely identify the issuing network operator.[10]/Service%20Docs/SL55_SIM.doc) If the MCC/MNC combination does not match the pre-programmed whitelist of allowed networks—usually set by the manufacturer at the carrier's request—the device enters a locked state, preventing network registration, calls, data access, or other services, and may display an error or prompt for an unlock code.[10][2] This verification occurs at the system-on-chip (SoC) or bootloader level, isolated from the main application processor, via the baseband firmware using proprietary protocols such as those for radio interface layer (RIL) communication or SIM authentication commands (e.g., APDU).[10] In some implementations, additional IMSI digits beyond MCC/MNC are cross-checked for finer granularity, enhancing security against partial matches./Service%20Docs/SL55_SIM.doc) The lock does not alter hardware capabilities like supported frequency bands but enforces exclusivity through this authentication failure, which persists even after device restarts until resolved. For CDMA devices, analogous mechanisms may tie the lock to the Electronic Serial Number (ESN) or Mobile Equipment Identifier (MEID) instead of IMSI, though GSM variants predominate in global discussions of SIM locking.[8] Functionally, the SIM lock serves to bind the device to the subsidizing carrier, recouping costs from discounted sales by deterring immediate resale or switching to competitors; unlocking typically requires a carrier-issued code, such as the Network Control Key (NCK), generated algorithmically from the phone's IMEI and the attempting SIM's IMSI, or via service mode access after meeting contractual terms like payment clearance.[10][8] Once entered correctly, the firmware disables the check, permitting use with any compatible SIM, though repeated failed attempts may trigger temporary blocks or permanent locks in some models to prevent brute-force attacks.[10] This process relies on non-standardized, vendor-specific algorithms, varying across manufacturers like Qualcomm or MediaTek SoCs, and can sometimes be bypassed through diagnostic modes or hardware interventions, underscoring its software-centric nature rather than tamper-proof hardware enforcement.[10]Distinction from Related Technologies
SIM lock restricts a mobile device to functioning exclusively with subscriber identity modules (SIMs) issued by a designated network operator, enforcing carrier-specific compatibility through firmware or software checks during SIM authentication. This mechanism differs fundamentally from SIM PIN protection, which is a security feature embedded in the SIM card itself, requiring entry of a user-defined personal identification number (typically 4-8 digits) to authorize cellular services like calls and data; failure to enter the correct PIN after multiple attempts locks the SIM, necessitating a PUK code from the carrier for recovery, but it applies regardless of the host device.[11][12] In contrast to IMEI blacklisting, where a device's international mobile equipment identity (IMEI) number is flagged in shared carrier databases—preventing network registration entirely due to reports of theft, loss, or unpaid contracts, even with a valid SIM from any operator—SIM lock permits operation on the subsidized carrier's network while blocking competitors, serving contractual retention rather than anti-theft enforcement.[13][14] SIM lock also stands apart from bootloader locking, a manufacturer-implemented safeguard that secures the device's boot process against unauthorized firmware modifications, rooting, or custom ROM installations to preserve system integrity and compliance with security certifications; a SIM-locked device may have an unlocked bootloader, allowing software alterations without resolving carrier restrictions, and vice versa.[15][16] Region locking, prevalent in devices like certain Samsung models to curb gray-market imports, confines functionality to the intended sales territory by verifying location via initial activations or calls within the region, potentially disabling cellular data or calls abroad even on SIM-unlocked hardware; unlike SIM lock's focus on operator exclusivity, region lock addresses geographic and regulatory variances, such as frequency bands or content licensing, and typically self-resolves after regional use.[17]Historical Development
Origins in Early Mobile Networks
In the era of first-generation (1G) analog mobile networks, such as AMPS deployed commercially in the United States starting October 1983, cellular phones lacked removable subscriber identity modules (SIMs). Authentication and network access relied on hardcoded electronic serial numbers (ESNs) and mobile identification numbers (MINs) embedded in the handset, effectively tying devices to specific carriers through hardware or firmware configurations rather than SIM-based restrictions.[18] The introduction of SIM locking coincided with the shift to second-generation (2G) digital networks, particularly the Global System for Mobile Communications (GSM), which standardized removable SIM cards for user authentication and network portability. The first commercial SIM cards were produced in 1991 by Giesecke+Devrient for Finland's Radiolinja operator, enabling the launch of the world's initial GSM network on July 1, 1991.[19] This innovation allowed subscribers to swap SIMs between compatible handsets but prompted carriers to implement software-based SIM locks to restrict subsidized devices to their networks, preventing immediate resale or use with competitors.[20] Early SIM locking served primarily to mitigate financial risks from handset subsidies, a common practice in nascent GSM markets where high device costs deterred adoption. By encoding network-specific keys into the phone's firmware, operators like those in Europe enforced contract terms, such as minimum service periods, before unlocking was permitted. This mechanism, absent in analog systems due to the lack of modular SIMs, marked a pivotal evolution in carrier control over mobile hardware.[20][21]Evolution with GSM and Beyond
The introduction of the Global System for Mobile Communications (GSM) in the early 1990s marked a pivotal shift in mobile telephony, standardizing removable Subscriber Identity Module (SIM) cards for user authentication and enabling interoperability across networks. However, this modularity prompted carriers to implement SIM locks as a countermeasure to protect investments in subsidized handsets, restricting devices to SIMs bearing specific International Mobile Subscriber Identity (IMSI) prefixes matching the carrier's Mobile Country Code (MCC) and Mobile Network Code (MNC). The first commercial GSM network launched on July 1, 1991, by Radiolinja in Finland, with initial deployments featuring software-based locks to enforce exclusivity amid rapid subscriber growth.[20] By 1998, global GSM subscribers exceeded 100 million, amplifying the use of SIM locks to mitigate customer churn in competitive markets.[20] As GSM evolved into 2.5G enhancements like General Packet Radio Service (GPRS) in 1999 and Enhanced Data rates for GSM Evolution (EDGE) around 2003, SIM locking mechanisms were refined to accommodate packet-switched data while preserving carrier-specific restrictions, often embedding checks in the phone's firmware against unauthorized SIMs. The transition to 3G Universal Mobile Telecommunications System (UMTS) in 2001 introduced Universal SIM (USIM) cards with enhanced cryptographic capabilities via the Authentication and Key Agreement (AKA) protocol, but locking persisted through similar IMSI validation, now supporting multimedia services and higher speeds. Carriers continued subsidizing devices, with locks extending to verify compatibility with UMTS frequency bands, thereby sustaining economic incentives for exclusivity into the mid-2000s.[22] The 4G Long-Term Evolution (LTE) rollout from 2009 onward maintained SIM lock fundamentals, adapting to IP-based architectures and Evolved Packet System (EPS) authentication, while 5G New Radio (NR) deployments since 2019 integrated 5G SIM or eSIM profiles with unified AKA procedures. Technically, locks evolved to handle multi-SIM and virtual provisioning in eSIMs, but regulatory interventions increasingly curtailed their enforcement. In the United States, the Federal Communications Commission (FCC) established policies in 2014 requiring carriers to unlock devices upon request after contract fulfillment or payment in full, with prepaid devices eligible after one year of activation.[23] European Union member states, guided by the 2005 Unfair Commercial Practices Directive, mandated free unlocking post-contract in many jurisdictions, reducing SIM locks' prevalence by the 2010s and promoting consumer mobility across borders.[24] These changes reflected empirical evidence of locks hindering competition, with unlocked devices facilitating lower-cost international roaming and prepaid alternatives.[25]Technical Implementation
Software-Based Locking
Software-based SIM locking refers to the implementation of carrier restrictions through programmable code embedded in the device's firmware or operating system, rather than irreversible hardware modifications. This approach enables the phone's baseband processor—a dedicated chipset handling cellular communications—to enforce compatibility checks on inserted SIM cards by reading and validating their embedded identifiers against preconfigured parameters supplied by the carrier or manufacturer.[23][26] The core enforcement occurs during SIM authentication or device boot sequences, where the software queries the SIM's International Mobile Subscriber Identity (IMSI), a unique 15-digit number stored on the card. The initial digits of the IMSI, comprising the Mobile Country Code (MCC, three digits) and Mobile Network Code (MNC, two or three digits), form the carrier's identifier, which the baseband firmware compares to a hardcoded or provisioned whitelist. If the values mismatch, the software blocks network registration, typically displaying an error such as "SIM network unlock PIN required" or "Invalid SIM," preventing voice, data, or SMS services while allowing emergency calls in many jurisdictions. For carrier-locked devices such as iPhones, initial activation similarly requires a SIM from the specific locking carrier; incompatible SIMs result in activation errors like "SIM not supported," necessitating verification of original purchase details or contact with the carrier for unlocking procedures.[26][10][27] This mechanism integrates with the phone's bootloader or system-on-chip (SoC) level software, often residing in the baseband modem's non-volatile memory, which operates semi-independently from the main application processor to ensure low-level control over radio functions. Carriers provision these locks remotely via over-the-air (OTA) updates or during manufacturing, associating the lock with the device's International Mobile Equipment Identity (IMEI) for traceability. Unlocking typically involves entering a network unlock code (NUC), an alphanumeric sequence derived algorithmically from the IMEI and carrier data, which reprograms the firmware to expand or remove the whitelist, rendering the lock inactive without altering hardware.[23][10] In modern smartphones compliant with 3GPP standards for GSM/UMTS/LTE networks, software locks may also incorporate Group Identifier (GID) checks from the SIM's elementary files for finer-grained restrictions, such as limiting to specific tariff plans within a carrier. This flexibility allows carriers to subsidize devices while recouping costs through contracts, but it introduces vulnerabilities to third-party code generation tools that exploit algorithmic weaknesses in NUC derivation, as documented in security analyses of pre-2010 implementations.[26] Unlike hardware variants, software-based systems facilitate compliance with regulations mandating unlockability after contract fulfillment, as seen in U.S. policies effective since 2014 requiring carriers to unlock post-payment devices upon request.[23]Hardware and Firmware Variants
The baseband processor, a specialized hardware component in mobile phones handling cellular communication protocols, serves as the primary enforcement mechanism for SIM locks. This chip operates independently of the main application processor and runs dedicated firmware that interrogates the SIM card's International Mobile Subscriber Identity (IMSI) upon insertion, comparing its mobile country code (MCC) and mobile network code (MNC)—the first five or six digits—against a hardcoded or stored whitelist of permitted networks before authorizing attachment.[28][29] Lock data, including permitted IMSI prefixes and unlock counters, is preserved in non-volatile storage such as NVRAM partitions or the device's Encrypted File System (EFS), which remain intact during operating system flashes or reboots but can be altered via carrier-provided codes that trigger firmware-level decryption or flag changes.[30][31] Hardware variants depend on the modem chip manufacturer; for instance, Qualcomm-based implementations often segregate lock settings in a distinct ROM chip or protected flash sector within the baseband SoC, rendering them inaccessible to standard software tools and necessitating proprietary flashing or hardware dongles for modification.[31] Firmware variants differ in verification logic and persistence: basic implementations rely on simple MCC/MNC matching, while advanced ones incorporate group identifiers (GID) or encrypted keys for multi-carrier support, with unlock attempts decrementing a counter that permanently disables the device after exhaustion.[26] Some firmware supports "fixed" modes, rigidly enforcing carrier-specific locks without user reconfiguration, whereas "active" modes allow temporary unlocks that revert upon factory reset, ensuring ongoing exclusivity.[32] These distinctions enhance resistance to third-party bypassing, as baseband firmware updates from manufacturers rarely expose lock parameters, preserving carrier control even on rooted devices.[33]Economic Rationale and Market Effects
Carrier Subsidies and Accessibility
Carriers subsidize mobile phones by offering them at prices below manufacturing and wholesale costs, typically recouping the difference through multi-year service contracts that generate ongoing revenue from usage fees and plans.[34] SIM locking enforces this model by restricting the device to the carrier's network, preventing customers from switching providers immediately after acquiring the subsidized hardware and thereby ensuring the carrier recovers its investment over the contract term.[5] Without such locks, subsidized devices could be resold or ported to competitors, undermining the economic viability of the subsidy and potentially leading carriers to eliminate discounts altogether.[35] This subsidy-lock mechanism enhances initial accessibility by reducing upfront costs for consumers, particularly those with limited financial resources who could not otherwise afford high-end smartphones at full retail prices—often exceeding $1,000 for flagship models.[36] For instance, in markets like Latin America, operators use subsidized locked handsets to drive digital inclusion, enabling broader adoption among underserved populations by bundling devices with affordable service plans.[37] Empirical analyses indicate that such arrangements have historically accelerated mobile penetration rates, as seen in early 2000s deployments where locked subsidized phones lowered barriers to entry compared to unlocked alternatives sold at premium prices.[38] However, SIM locks can diminish long-term accessibility by limiting device portability, complicating switches to carriers with superior coverage or pricing and restricting use with international SIMs for travelers.[16] In the United States, prior to widespread unlocking policies implemented around 2014, locked subsidized phones tied an estimated 80-90% of postpaid subscribers to their original carriers during contract periods, potentially exacerbating coverage gaps in rural or competitive markets.[8] While subsidies expand access at purchase, the lock's enforcement of exclusivity may indirectly favor larger incumbents, reducing competitive incentives for service improvements that could otherwise enhance overall consumer accessibility.[39]Incentives for Exclusivity Deals
Carriers engage in exclusivity deals for handsets to secure sole distribution rights, enabling them to offer desirable devices unavailable from competitors and thereby capture targeted customer segments. These arrangements typically pair with device subsidies, where the carrier absorbs much of the upfront cost to lower barriers for consumers, recouping investments through multi-year service contracts. SIM locking enforces retention by restricting the device to the carrier's network, imposing switching costs that discourage early termination and ensure revenue from voice, data, and ancillary services over the contract period.[40][41] Such exclusivity incentivizes carriers to invest heavily in marketing and promotions for the locked device, fostering brand loyalty and differentiating their portfolio in saturated markets. By limiting supply to one provider, carriers can command premium pricing on service plans bundled with the handset, as consumers prioritize access to the exclusive model over alternatives. This dynamic aligns with economic models where exclusive dealing softens price competition among carriers while creating incentives for aggressive subscriber acquisition, potentially boosting long-term profits despite initial subsidy outlays.[42] A prominent example is AT&T's exclusive U.S. agreement with Apple for the iPhone starting in June 2007, which subsidized the device at $499 for the base model under a two-year contract while SIM-locking it to AT&T's network. This deal propelled AT&T's subscriber growth, as the iPhone's appeal drew customers willing to commit to higher-rate plans, allowing the carrier to offset exclusivity payments to Apple through elevated average revenue per user from data-heavy usage. Empirical analysis of this arrangement indicates that carriers adjust pricing and subsidies in response to exclusivity, enhancing their competitive positioning without necessarily harming overall market entry dynamics.[43][40]Empirical Impacts on Competition and Adoption
Empirical studies indicate that SIM locks elevate switching costs for consumers, thereby constraining carrier competition. In Japan, a 2010 analysis using web-based stated preference surveys estimated that SIM card locks contributed substantially to lock-in effects, with over 80% of respondents valuing unlocked compatibility highly; subsequent SIM unlock policies demonstrably lowered these costs, facilitating easier carrier changes and implying reduced competitive pressure under locking regimes.[44] Similarly, econometric models of mobile markets highlight how such locks amplify inertia, limiting churn and enabling incumbents to sustain premiums without aggressive rivalry.[45] Countervailing evidence suggests limited anticompetitive harm from SIM locks. A 2024 economic assessment found no discernible impact on churn rates attributable to locking practices, arguing that consumer mobility remains robust despite locks, as evidenced by stable switching behaviors in locked U.S. markets; mandatory unlocking, while trivial in procedural cost (averaging minutes per request), risks eroding carrier incentives without commensurate competition gains.[39] Regulatory proposals for shorter lock periods, such as the U.S. FCC's 60-day limit, posit enhanced rivalry and lower prices, yet lack preemptive empirical validation beyond theoretical switching cost reductions.[46] Regarding adoption, SIM locks underpin handset subsidies that broaden access, particularly for cost-sensitive users. By tying discounted devices to service contracts, locks allow carriers to recoup costs over time, spurring penetration in subsidized markets; empirical patterns in locked regimes, like the U.S., correlate with rapid uptake among low-income cohorts, where full-price alternatives would deter entry.[39] Unlocking mandates may curtail these subsidies, potentially slowing adoption in emerging or price-elastic segments, as carriers shift burdens to higher upfront fees without offsetting welfare gains from portability.[44]Unlocking Methods and Risks
Official Carrier Unlocking Procedures
Official carrier unlocking procedures typically require consumers to contact the original service provider to verify eligibility and request the unlock, which may involve providing an unlock code, software-based remote activation, or firmware update depending on the device and carrier policies. Eligibility often hinges on factors such as the device being fully paid off, the account being in good standing without outstanding balances or fraud flags, and a minimum activation period—commonly 40 to 60 days in the United States, though proposals exist to standardize this at 60 days regardless of payment status.[23][47] Carriers are generally obligated to unlock eligible devices free of charge under voluntary commitments or regulatory pressure, but processing times can vary from immediate remote unlocks to several business days for code delivery.[8] The standard process begins with confirming the device's lock status: on iPhones, users check Settings > General > About for "Carrier Lock" indicating restrictions; Android devices may require dialing *#06# to view IMEI and carrier details or using apps to detect locks.[27][48] For iPhones bound to US operators such as Verizon or AT&T, unlocking involves contacting the carrier with the IMEI for verification of full payment and account status, which can be challenging for second-hand buyers lacking original account access. Once verified, consumers submit requests through the carrier's online portal, app, customer service hotline, or in-store support, providing proof of purchase, account details, and IMEI number. For example, T-Mobile requires eligible devices to be active on their network for at least 40 days (or 365 days for military deployments) before processing unlocks via contact form or support, often resulting in automatic software unlocks without codes for compatible models.[49] AT&T processes unlocks over-the-air for eligible postpaid iPhones after 60 days of activation and full payment, without requiring an unlock code; users complete the process by connecting to Wi-Fi or using iTunes/Finder to back up and restore the device. For other eligible devices, unlock codes are provided, instructing users to insert a non-AT&T SIM and enter the code when prompted.[50][51]- Step 1: Verify eligibility – Ensure the device meets carrier criteria, such as no unpaid balances and compliance with service terms; carriers like Verizon automatically unlock devices 60 days post-activation for paid-off models.[48]
- Step 2: Submit request – Use carrier-specific tools; Straight Talk, for instance, allows online checks and requests via their portal after 12 months of service for qualifying plans.[52]
- Step 3: Receive and apply unlock – For code-based unlocks, insert a non-carrier SIM to trigger the prompt; software unlocks may occur over-the-air without user intervention.[23]
- Step 4: Confirm unlock – Re-check status or test with another SIM; failed attempts (e.g., exceeding code tries) can permanently lock the device.[51]
