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Threema
DeveloperThreema GmbH
Initial releaseDecember 2012 (2012-12)[1]
Stable release(s)
Android6.2.1-1098[2] Edit this on Wikidata / 13 November 2025
iOS4.6.17[3] Edit this on Wikidata / 14 March 2022
Desktop1.2.0[4] Edit this on Wikidata / 27 March 2022
Written inObjective-C (iOS), Java (Android), C, .NET (Windows Phone)
Operating systemiOS, Android, Windows Phone
Available inEnglish, German, French, Spanish, Italian, Russian, Brazilian Portuguese, Polish, Rumantsch Grischun
TypeEncrypted instant messaging & voice calling
LicenseAndroid client: AGPL-3.0-only
iOS client: AGPL-3.0-only
Web client: AGPL-3.0-or-later[5]
Protocol: MIT[6]
Server: Proprietary
Websitethreema.ch

Threema is a paid cross-platform encrypted instant messaging app developed by Threema GmbH in Switzerland and launched in 2012. Users can make voice and video calls, send photos, files, and voice notes, share locations, and join groups. The service offers end-to-end encryption. Unlike many other popular secure messaging apps, Threema does not require phone numbers or email addresses for registration, only a one-time purchase that can be paid via an app store or anonymously with Bitcoin or cash.[7]

Threema is available on Android and iOS, and has clients for HarmonyOS, Linux, macOS Windows and can be accessed via web browser, but requires a mobile app to function.[8]

Features

[edit]

The service claims to be based on the privacy by design principles by not requiring a phone number or other personally identifiable information. This helps anonymize the users to a degree.[9][10]

Threema uses a randomly generated user ID, created after the initial app launch, instead of requiring a linked email address or phone number to send messages. It is possible to find other users by phone number or email address, if the user allows the app to synchronize their address book.[11]

Linking a phone number or email address to a Threema ID is optional. Hence, the service can be used anonymously.

Users can verify the identity of their Threema contacts by scanning their QR code when they meet in person. The QR code contains the public key of the user, which is cryptographically tied to the ID and will not change during the lifetime of the identity.

Using this strong authentication feature, users can make sure they have the correct public key from their chat partners, which provides additional security against a man-in-the-middle attack.

Threema classifies contacts according to three verification trust levels. The verification level of each contact is displayed in the Threema application as dots next to the corresponding contact.

In addition to text messaging, users can make voice and video calls, share locations, voice messages, and send media or other files.[12] A web app, Threema Web, can be used on desktop devices, but only as long as the phone with the Threema installation of the user is online. There is a beta for iOS users, which allows for the phone to be offline while using a desktop app.

In addition to one-to-one chats, Threema offers group chats with up to 256 people. Files are limited to 50MB per file.[12][13] It is also possible to create polls in personal or group chats.[14]

To emulate the 'Saved Messages' feature available in other messengers, one can created a group with only oneself as a member. For licensing and privacy reasons, Threema does not include a GIF library natively, but it is compatible with GIF keyboards and plays animations seamlessly in the chat.

Software

[edit]

Threema is developed by the Swiss company Threema GmbH.[15] The servers are in Switzerland and the development is based in Pfäffikon SZ. As of May 2021, Threema had 10 million users[16] and the business version, Threema Work, was used by 2 million users across 5,000 companies and organizations.[17]

At the end of July, 2021 Threema introduced the ability for companies to host the messenger on their own server, primarily intended for companies with significantly high privacy concerns.[18]

Clients

[edit]

With Threema Web, a client for web browsers, Threema can be used from other devices like desktop computers, though only as long as the original device is online.

Threema optionally supports Android Wear smartwatch and Android Auto.[19] Threema launched support for end-to-end encrypted video calls on August 10, 2020. The calls are person-to-person with group calls unavailable.[20]

The application does not allow the self-deletion of messages after a period defined by the interlocutors. The application does prevent screenshots in conversations when configured to do so.

Architecture

[edit]

The entire communication via Threema is end-to-end encrypted. During the initial setup, the application generates a key pair and sends the public key to the server while keeping the private key on the user's device.[21] The application then encrypts all messages and files that are sent to other Threema users with their respective public keys.[9][22] Once a message is delivered successfully, it is immediately deleted from the servers.[23]

The encryption process used by Threema is based on the open-source library NaCl library. Threema uses asymmetric ECC-based encryption, with 256-bit strength. Threema offers a "Validation Logging" feature that makes it possible to confirm that messages are end-to-end encrypted using the NaCl Networking and Cryptography library.[24]

In August 2015, Threema was subjected to an external security audit.[25] Researchers from cnlab confirmed that Threema allows secure end-to-end encryption, and claimed that they were unable to identify any weaknesses in the implementation.

Cnlab researchers also confirmed that Threema provides anonymity to its users and handles contacts and other user data as advertised.[26][27]

History

[edit]

Threema was founded in December 2012 by Manuel Kasper.[28] The company was initially called Kasper Systems GmbH.[29] Martin Blatter and Silvan Engeler joined Kasper to develop an Android application that was released in early 2013.[30]

In Summer 2013, the Snowden leaks helped create an interest in Threema, boosting the user numbers to the hundreds of thousands.[31] When Facebook took over WhatsApp in February 2014, Threema got 200,000 new users, doubling its userbase in 24 hours.[32] Around 80% percent of those new users came from Germany. By March 2014 Threema had 1.2 million users.[30]

In Spring 2014, operations were transferred to the newly created Threema GmbH.[29][33] Martin Blatter took over the position of CEO.[34]

In December 2014, Apple listed Threema as the most-sold app of 2014 at the German App Store.[35]

In 2020, Threema expanded with video calls,[20] plans to open-source its client-side apps and introduce reproducible builds of them,[36] as well as introduce Threema Education, a variation of Threema intended for education institutions.

In September 2020, Threema was acquired by AFINUM, a German private equity firm based in Munich.[37]

During the second week of 2021, Threema saw a quadrupling of daily downloads spurred on by controversial privacy changes in the WhatsApp messaging service. A spokesperson for the company also confirmed that Threema had risen to the top of the charts for paid applications in Germany, Switzerland, and Austria.[38] This trend continued into the third week of the year, with the head of Marketing & Sales confirming that downloads had increased to ten times the regular amount, leading to "hundreds of thousands of new users each day".[39]

In October 2022, researchers from ETH Zurich reported multiple vulnerabilities affecting Threema's security against network, server and client-based attacks. A new release fixing these issues was released in November 2022 and the vulnerabilities were announced publicly in January 2023.[40]

In September 2024, CEO Martin Blatter and the remaining founders and original developers left the company and Robin Simon, a former executive from TX Group became CEO.[41][42]

[edit]

Threema Work

[edit]

On May 25, 2016, Threema Work, a corporate version of Threema, was released. Threema Work offers extended administration and deployment capabilities.[43] Threema Work is based on a yearly subscription model.[44]

Threema Gateway

[edit]

On March 20, 2015, Threema released a gateway for companies. Similar to an SMS gateway, businesses can use it to send messages to their users who have Threema installed.[45] The code for the Threema Gateway SDK is open for developers and available on GitHub.[46]

Threema Broadcast

[edit]

On August 9, 2018, Threema released Threema Broadcast, a tool for top-down communication. Similar to emails in electronic newsletters, Threema messages can be sent to any number of feed subscribers, and the Threema Broadcast allows to create chatbots.

Threema Education

[edit]

On September 10, 2020, Threema released Threema Education, a version of its messenger designed for education institutions. The app integrates Threema Broadcast and requires a one-time payment for each device used. It's intended for use by teachers, students, and parents.[47]

Threema OnPrem

[edit]

On July 27, 2021, Threema released Threema OnPrem, a version of the messenger which could be hosted on a company's own servers for maximum security purposes.[48]

Privacy

[edit]

Since Threema's servers are in Switzerland, they are subject to the Swiss federal law on data protection. The data center is ISO/IEC 27001-certified.[49]

Linking a phone number and/or email address to a Threema ID is optional; when doing so, only checksum values (SHA-256 HMAC with a static key) of the email address and/or phone number are sent to the server.[50]

Due to the small number of possible digit combinations of a telephone number, the phone number associated with a checksum could be determined by brute force. The transmitted data is TLS-secured. The address book data is kept only in the volatile memory of the server and is deleted immediately after synchronizing contacts.[51]

If a user chooses to link a phone number or email address with their Threema ID, they can remove the phone number or email address at any time.[52] Should a user ever lose their device (and their private key), they can revoke their Threema ID if a revocation password for that ID has been set.[53]

Groups are solely managed on users’ devices and group messages are sent to each recipient as an individual message, encrypted with the respective public key. Thus, group compositions are not directly exposed to the server.[54]

Data (including media files) stored on the users’ devices is encrypted with AES 256. On Android, it can be additionally protected by a passphrase.[55]

Since 2016, Threema GmbH publishes a transparency report where public authority inquiries are disclosed.[56]

On March 9, 2017, Threema was listed in the "Register of organizers of information dissemination in the Internet" operated by the Federal Service for Supervision of Communications, Information Technology and Mass Media of the Russian Federation.[57]

In a response, a Threema spokesperson publicly stated:[58]

"We operate under Swiss law and are neither allowed nor willing to provide any information about our users to foreign authorities."

On April 29, 2021, Threema won a significant case at the Federal Supreme Court of Switzerland against the Swiss Federal Department of Police and Justice, who wished to classify the company as a telecommunications provider. Had they lost the case, Threema would have had a legal requirement to identify users and send information about their users to law enforcement.[59]

Starting January 2022, Swiss Armed Forces suggested that the troops should use Threema instead of WhatsApp, Telegram and Signal, citing Threema being Swiss-based without servers in the United States and thus not subject to the CLOUD Act, also promising that soldiers would be reimbursed for the cost.[60]

Reception

[edit]

In February 2014, German consumer organisation Stiftung Warentest evaluated several data-protection aspects of Threema, WhatsApp, Telegram, BlackBerry Messenger and Line.

It considered the security of the data transmission between clients, the services' terms of use, the transparency of the service providers, the availability of the source code, and the apps' overall availability.

Threema was the only app rated as 'non-critical' (unkritisch) in relation to data and privacy protection, but lost marks due to its closed-source nature, though this has changed for its frontend clients since the end of 2020.[61]

Along with Cryptocat and Surespot, Threema was ranked first in a study evaluating the security and usability of instant messaging encryption software, conducted by the German PSW Group in June 2014.[62]

As of November 2015, Threema had a score of 6 out of 7 points on the – now withdrawn and outdated – Electronic Frontier Foundation's "Secure Messaging Scorecard". It received points for having communications encrypted in transit, having communications encrypted with keys the provider doesn't have access to (i.e. having end-to-end encryption), making it possible for users to independently verify their correspondent's identities, having past communications secure if the keys are stolen (i.e. implementing forward secrecy), having its security design well-documented and having completed an independent security audit.

It lost a point because its source code was not open to independent review (i.e. it was not open-source, though in late 2020 its client apps were open-sourced, leaving only its server daemons proprietary).[63]

Since May 2023, Threema and several other encrypted messaging apps are banned in India for their alleged use by terrorists.[64][65]

See also

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References

[edit]
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Threema

View on Grokipedia
from Grokipedia

Threema is a paid instant messaging application developed by Threema GmbH, a company based in Switzerland, launched in 2012 with a focus on user privacy and security.
Unlike many competitors, it does not require a phone number or email address for registration, instead assigning users a randomly generated Threema ID to enable anonymous communication.
The app employs end-to-end encryption for all messages, voice and video calls, group chats, and file transfers, utilizing open-source cryptographic protocols, with servers hosted exclusively in Switzerland to leverage strict data protection laws.
Threema avoids data collection for advertising purposes and offers no free tier reliant on user tracking, positioning it as a premium alternative in the secure messaging market.
However, a 2023 peer-reviewed analysis by researchers at ETH Zurich identified seven cryptographic vulnerabilities in Threema's protocols, enabling potential attacks such as message decryption or impersonation under specific threat models, prompting debates over its security claims despite subsequent patches.

Company and Development

Founding and Ownership

Threema, a secure messaging application emphasizing and user privacy, originated in in late 2012 when software developer Manuel Kasper initiated its development as an independent alternative to mainstream apps like , initially under the entity Kasper Systems . The app's beta version was released on December 13, 2012, for , followed by Android shortly thereafter, driven by Kasper's focus on implementing robust cryptographic protocols from the outset without reliance on external servers for . In spring 2014, Threema GmbH was formally established in Pfäffikon, , to support the app's commercial expansion, with Kasper joined by fellow developers Silvan Engeler and Martin Blatter as co-founders. These three individuals, all Swiss software engineers, retained operational control and shaped the company's commitment to Swiss data protection laws and minimal practices. Threema GmbH operated as a privately held entity until September 2020, when Swiss investment firm AFINUM Partners AG acquired a majority stake to fund further growth while preserving the founders' vision of privacy-centric development. The original founders—Kasper, Engeler, and Blatter—continued in leadership roles, maintaining a significant minority ownership interest to ensure alignment with core principles such as open-source client code and server-side transparency reports. In January 2026, German private equity firm Comitis Capital announced an agreement to acquire Threema Holding AG from AFINUM Partners AG and the founders, with closure expected in the same month. Comitis Capital committed to supporting Threema's growth and international expansion while preserving management continuity, the privacy-by-design philosophy, open-source software, and Swiss sovereignty. Threema remains funded primarily through paid subscriptions.

Business Model and Sustainability

Threema's consumer-facing application requires a one-time purchase of approximately 4 to 6 Swiss francs (or equivalent, varying by and region), providing users with permanent access, including all updates, without subscriptions, advertisements, or data-based revenue streams. This model contrasts with ad-supported or alternatives by prioritizing user over surveillance , as the company explicitly avoids tracking, profiling, or selling . For businesses, Threema offers Threema Work, a subscription-based enterprise edition with tiered plans such as Core at about 3 USD per user per month, incorporating features like centralized user management, on-premises hosting options, and compliance tools for . Additional services, including Threema Broadcast for one-to-many messaging, generate further revenue through scalable licensing. This recurring enterprise income supplements one-time consumer sales, funding server maintenance, cryptographic enhancements, and staff of around 50 employees as of recent reports. Founded in 2012 by Manuel Kasper, Silvan Engeler, and Martin Blatter as an independent Swiss entity, Threema initially self-funded through app purchases, achieving profitability without or data monetization. In September 2020, Afinum Management, a Swiss , acquired a stake for undisclosed terms, while founders retained a significant minority holding to preserve strategic control and privacy commitments. This infusion supported international expansion and open-sourcing initiatives without shifting to growth-at-all-costs metrics. Sustainability derives from lean operations, data minimization principles that reduce infrastructure demands, and a position emphasizing and Swiss jurisdiction for regulatory appeal in privacy-sensitive sectors. Operating profitably for over 12 years amid competition from free apps like Signal or underscores the model's resilience, though growth remains constrained by the paid barrier; enterprise adoption and periodic feature expansions mitigate this by diversifying revenue without compromising core tenets.

Technical Architecture

Client Applications

Threema provides native client applications for Android and mobile operating systems, desktop environments including Windows, macOS, and , and a browser-based web client. All clients require an initial setup with a paid purchased through the respective app stores or official channels, enabling end-to-end encrypted communication without mandatory phone number or email registration. The Android client, distributed via the Google Play Store, supports features such as voice and video calls, file sharing up to 50 MB, and integration with device storage for media handling. It is also available in a libre variant called Threema Libre through F-Droid for users avoiding proprietary repositories, though this version necessitates manual license activation. The iOS client, obtainable from the Apple App Store, mirrors these capabilities with iOS-specific optimizations like integration with iMessage-style notifications and support for Live Photos and location sharing. Desktop clients for Windows, macOS, and offer native applications that synchronize fully with the linked via a one-time scan, providing access to all messages, contacts, and media without retaining data on servers post-decryption. These apps, developed using frameworks like for cross-platform compatibility, include offline message queuing and multi-device session management. In contrast, the Threema Web client operates directly in supported browsers such as Chrome and , requiring the same pairing for setup and emphasizing temporary session data that clears upon logout or browser closure to minimize persistent storage risks. Both desktop and web interfaces prioritize keyboard-driven workflows and larger screen layouts for efficient group management and file previews.

Cryptographic Protocols

Threema implements a dual-layer encryption system for all communications, comprising an (E2EE) layer between sender and recipient, and a between clients and servers. The E2EE layer ensures that only the intended recipients can decrypt messages, while the protects data in transit to prevent server-side interception. This design leverages open-source from the NaCl (Networking and Cryptography library), prioritizing security, performance, and minimal message overhead. The core E2EE protocol for one-to-one messaging uses Diffie-Hellman (ECDH) key exchange based on for generating shared secrets from users' long-term public-private key pairs. Each user generates a unique key pair upon initial app setup, with the private key stored securely on the device and the public key uploaded to Threema's directory server for discovery via Threema IDs. Messages are then authenticated and encrypted using XSalsa20 combined with Poly1305 (MAC), forming an scheme resistant to chosen-ciphertext attacks. Key derivation employs BLAKE2b and HSalsa20 functions to produce session keys from the ECDH shared secret. To address limitations in the original protocol, such as the absence of perfect (PFS), Threema introduced the protocol in December 2022, which became the default for E2EE messaging by 2023. incorporates pairs and a mechanism to achieve PFS, ensuring that compromise of long-term keys does not retroactively expose prior sessions. A formal security proof conducted by researchers at the University of Erlangen-Nuremberg in 2023 verified 's , , authenticity, and PFS properties, demonstrating that protocol breaches would require solving the Gap Diffie-Hellman problem in polynomial time—an assumption widely held to be computationally infeasible.
ComponentAlgorithm/MethodPurpose
Asymmetric Key Exchange ECDHShared secret derivation between long-term keys
Symmetric EncryptionXSalsa20Message confidentiality
AuthenticationIntegrity and authenticity
Key DerivationBLAKE2b, HSalsa20Session key generation
PFS Mechanism ratcheting with ephemeral keysForward secrecy for sessions
Group communications extend the E2EE model by individually encrypting messages to each member using their public keys, without a shared group key, to maintain deniability and avoid single points of failure. Multimedia files are encrypted with random 256-bit symmetric keys, themselves E2EE-protected during transmission. Independent analyses prior to Ibex, such as a 2023 Security paper, identified vulnerabilities in earlier protocol variants, including cross-protocol attacks and key reuse issues, which Threema mitigated through Ibex's redesign. The whitepaper, last updated March 13, 2025, confirms ongoing reliance on these primitives with no reported breaches in the audited Ibex .

Server Infrastructure and Data Flow

Threema maintains its primary server infrastructure in , operating from two high-security data centers in the area under an ISO 27001-certified colocation partner. The system employs three server categories: chat servers using a custom TCP-based protocol for message transport with perfect via ephemeral keys per connection; directory servers handling user public keys and Threema IDs over ; and media servers managing encrypted file uploads and downloads also via with TLS 1.3 and public-key pinning. While the core server software remains and centralized for the standard service, Threema offers an OnPrem variant for self-hosted deployments, allowing organizations to run compatible infrastructure on their own hardware with full data control. Message data flow in Threema prioritizes , with servers functioning solely as relays without access to content. Clients initiate secure client-to-server (C2S) channels through a protocol using long-term identity keys ( ECDH) and ephemeral keys to derive session keys, layering transport encryption (XSalsa20-Poly1305) over for messages in transit. Upon sending, a client encrypts the message payload for the recipient's public key, forwards the double-encrypted blob to a chat server, which routes it to the recipient's connected device or buffers it briefly if offline; no persistent message storage occurs on servers post-delivery. Group messages are individually encrypted to each member's key and sent separately, rendering group structures opaque to servers. Directory servers retain minimal data, including public keys and 8-character Threema IDs assigned randomly upon user registration, but store no address book hashes or persistent message histories. Encrypted media files are uploaded to media servers with a one-time 256-bit symmetric key shared via end-to-end encrypted text, with temporary storage limited to 14 days before deletion. Metadata such as sender/recipient IDs and timestamps is logged transiently for , though servers claim no linkage of backups to identities beyond potential IP correlations. Multi-device support involves a mediator server proxying encrypted sync messages between linked devices via QR-code-based key exchanges, ensuring content remains inaccessible to intermediaries. This architecture minimizes server-side , aligning with Swiss privacy standards, though analyses note vulnerabilities to long-term key compromises enabling retrospective decryption of stored ciphertexts.

Core Features

Messaging Capabilities

Threema supports sending and receiving text messages in both one-on-one chats and group conversations, with all communications secured through using the NaCl library and protocols such as and perfect forward secrecy. Messages include status indicators showing whether they have been sent (single checkmark), delivered to the recipient's device (double checkmark), or read (double checkmark with an eye icon or similar visual cue). These read receipts are optional and can be disabled globally via app settings or overridden on a per-contact basis to prevent metadata leakage about message consumption. The app also features typing indicators that alert users when a contact is actively composing a response, promoting natural conversation flow while allowing users to disable this for individual contacts or entirely to minimize unintended disclosures. As of August 12, 2024, Threema introduced the ability to edit sent text messages or delete them for all parties involved, including on the recipient's device, provided both users have updated to compatible app versions; edited messages display a note indicating changes, preserving transparency. This functionality applies to text messages but excludes certain types like polls or system messages. Voice messaging complements text capabilities, enabling users to record and send short audio clips that are similarly end-to-end encrypted and support the same receipt statuses. Unlike some competitors, Threema does not offer built-in self-destructing messages with custom timers, prioritizing server-independent encryption over ephemeral features that could introduce additional protocol complexities.

Group and Multimedia Functions

Threema enables group chats with up to 256 participants, where messages are exchanged among members in a decentralized manner managed entirely on individual devices. Threema's servers maintain no records of group compositions or memberships, enhancing by preventing centralized oversight of participant details. All group messaging is secured via , ensuring that only intended recipients can access content. Within groups, users can conduct end-to-end voice and video calls initiated directly from the chat interface, supporting real-time audio and video communication among members. Group polls allow administrators to collect responses efficiently, with results aggregated privately among participants. Distribution lists provide an alternative for one-way to multiple contacts without enabling replies, distinct from interactive groups. sharing in Threema includes transmission of photos, videos, voice messages, files in any format up to 100 MB per file, and location data, all protected by end-to-end to prevent interception or server access. Videos can be compressed via app settings to optimize for the size limit, while files exceeding device memory constraints may fail to send on older hardware. Locations are shared as static points or live updates, integrated seamlessly into chats or groups.

Privacy and Anonymity Tools

Threema enables user primarily through its Threema ID system, a randomly generated 8-character alphanumeric identifier assigned upon app installation, which serves as the sole means of identification without requiring a phone number, , or any for registration. This design contrasts with apps that mandate verifiable identifiers, allowing users to maintain complete detachment from real-world details unless they opt to link such information voluntarily for contact discovery. As a result, Threema , the Swiss-based developer, states it has no inherent knowledge of users' identities, as no central database ties IDs to personal attributes absent user-initiated associations. To preserve , Threema minimizes server-side and avoids automatic contact syncing; users must explicitly enable features that hash and transmit phone numbers or emails for syncing, which can be skipped entirely. Contact verification occurs via direct scanning between devices, bypassing server mediation and reducing metadata exposure. The app also supports anonymous group creation and participation, where initiators can generate links without revealing sender details, and features like polls ensure voter responses remain unlinked to participants' IDs. Threema eschews self-destructing messages, citing their unreliability due to recipients' ability to or copy content before deletion, opting instead for local message storage and user-controlled deletion tools, such as bulk chat cleanup or automatic archival after inactivity periods. Backups via Threema Safe use end-to-end encrypted, user-held keys stored separately, preventing server access even if enabled. These mechanisms collectively prioritize sustained over ephemeral features that could foster a false sense of security.

Historical Development

Inception and Early Launch (2012–2015)

Threema was conceived in 2012 by three young Swiss software developers seeking to create an independent messaging application for among friends, at a time when mainstream apps like lacked robust . The initial development effort was led by Manuel Kasper, who authored the first version amid growing concerns over message interception and data sharing in existing platforms. The app's inaugural release occurred on December 12, 2012, with the version debuting in Apple's under the name "Threema," followed promptly by an Android counterpart. From launch, Threema operated as a paid service without advertising or user data collection, prioritizing via the NaCl library and optional user anonymity through randomly generated IDs rather than phone numbers or emails. Early adoption remained modest until early 2014, when Facebook's acquisition of triggered widespread privacy apprehensions, propelling Threema's user base from hundreds of thousands to over 2 million within weeks. This surge underscored the app's appeal as a Swiss-based alternative emphasizing server-side deletion post-delivery and minimal metadata retention. By mid-2015, Threema expanded into the U.S. market, marketing its features to users wary of amid discussions of apps' roles in . During this period, the company, , focused on cross-platform compatibility and iterative enhancements, establishing a foundation for its no-subscription, one-time-purchase model that avoided reliance on user data monetization.

Growth Phases and Milestones (2016–2020)

In 2016, Threema launched Threema Work, an enterprise-oriented version of its messenger tailored for companies, public authorities, and organizations, emphasizing user-friendliness alongside stringent data protection to meet emerging regulatory demands. This marked a shift toward professional markets, building on the app's consumer base established since 2012. By 2017, Threema expanded its feature set with the introduction of Threema Web for desktop-based chatting and end-to-end encrypted voice calls that did not require disclosing phone numbers, enhancing usability without compromising anonymity. These additions supported gradual user adoption amid growing privacy concerns in Europe, though exact quarterly growth figures remain undisclosed by the company. The enactment of the EU's General Data Protection Regulation (GDPR) in 2018 propelled demand for Threema Work, as organizations sought compliant communication tools; concurrently, Threema released Broadcast for one-to-many messaging and Safe for encrypted backups. User base expansion continued steadily, reflecting Threema's positioning as a privacy-focused alternative to dominant apps like WhatsApp. In 2019, an independent security audit by the validated the robustness of Threema's core app and Threema , affirming its cryptographic integrity against common vulnerabilities. This external verification bolstered credibility among enterprise adopters. By January 2020, Threema's overall user base surpassed 8 million, including over 2 million Threema Work users across approximately 5,000 organizations. That year, the company secured from Afinum to ensure long-term stability and development, while adding end-to-end encrypted video calls in response to heightened remote communication needs during the emerging ; additionally, on September 10, Threema Education was released, adapting the platform for educational institutions with integrated broadcast features.

Recent Updates and Events (2021–2025)

In 2021, Threema launched OnPrem, a self-hosted version of its messaging platform designed for organizations seeking full control over data and infrastructure, enabling deployment on private servers to enhance and compliance. This release addressed demands from enterprise users for on-premises solutions amid growing concerns over cloud-based data storage. A significant event occurred in January 2023 when researchers from published an analysis at the Security Symposium, identifying seven cryptographic vulnerabilities in Threema's protocols, including issues with key separation, side-channel attacks on private key recovery, and flaws in mechanisms that could enable message decryption or impersonation under specific threat models. The findings, detailed in a peer-reviewed paper, highlighted risks such as lack of proper and recoverable from past sessions in certain scenarios, though the researchers noted these required advanced adversary capabilities. Threema responded officially, asserting that the alleged weaknesses had no real-world impact due to mitigations in implementation and that no exploits were demonstrated against deployed systems, while committing to protocol reviews without admitting exploitable flaws. In April 2024, Threema showcased its OnPrem solution at the GISEC Global cybersecurity exhibition in , emphasizing self-hosting capabilities for and integration with enterprise environments. This event underscored the platform's appeal to sectors prioritizing operational independence from third-party servers. Throughout 2025, Threema continued iterative updates, including a June 5 release for Threema Broadcast (version 2.24.0) featuring a refreshed , updated aligning with corporate , and general performance enhancements with bug fixes. Concurrently, proposed amendments to Switzerland's Surveillance Act (VÜPF) drew scrutiny, with the Federal Council initiating in January 2025 to expand access, potentially requiring encrypted services like Threema to implement user identification, metadata retention, and decryption backdoors—measures critics likened to authoritarian precedents and which Threema's model, reliant on minimal , would complicate. The consultation concluded in May 2025 amid opposition from privacy advocates, highlighting tensions between imperatives and Switzerland's reputation for data protection.

Security and Privacy Analysis

Encryption Mechanisms and Audits

Threema employs for all messages, calls, and file transfers, utilizing the NaCl (Networking and Cryptography) library's crypto_box primitive. This implementation leverages Diffie-Hellman for asymmetric , XSalsa20 for symmetric , and Poly1305 for message authentication, providing 255-bit equivalent strength. Each user generates a unique key pair upon app installation, with the public key forming part of their anonymous Threema ID; messages are encrypted directly to the recipient's public key without server involvement in decryption. A separate transport layer secures client-server communication using analogous NaCl mechanisms, ensuring data confidentiality even if intercepted en route. Prior to 2022, the protocol used static long-term keys for ongoing sessions, omitting forward secrecy and relying on bidirectional X25519 key derivation without ephemeral keys or ratcheting. This design facilitated persistent access to past messages if a private key were compromised post-session. In December 2022, Threema deployed the Ibex protocol to address these limitations, incorporating X3DH for initial key establishment, a double-ratchet mechanism for forward secrecy and post-compromise security, and Noise Protocol Framework elements for handshake security. Ibex applies per-message ephemeral keys and symmetric ratcheting to derive session keys, mitigating key reuse and enabling secure key rotation. Threema's codebase, being open-source since 2015, has undergone multiple third-party audits. In October 2020, Cure53 assessed the and Android apps, identifying 12 vulnerabilities (primarily implementation flaws like improper input validation and side-channel risks) rated medium to high severity, all of which Threema remediated prior to public release of the report. Further Cure53 reviews in targeted Rust-based crypto libraries, uncovering minor issues in key handling fixed in subsequent updates, and in 2024 examined the desktop app, finding no critical flaws but recommending UI hardening. An independent analysis by researchers, published at Security 2023, scrutinized the pre- protocols and demonstrated seven cryptographic attacks across three threat models, including cross-protocol key recovery (allowing impersonation via downgrades), lack of indistinguishability against chosen-ciphertext attacks, and offline recovery of messages from compromised devices without . Proof-of-concept exploits confirmed practical feasibility under realistic assumptions, such as server compromise or device theft, though no widespread real-world exploitation was reported. Threema's rollout of predated the full paper but aligned with early findings; a commissioned 2023 of verified its resistance to standard attacks like key-compromise impersonation and provided formal proofs for core properties under the Dolev-Yao model. Threema characterized the findings as having limited practical impact due to mitigations like device-bound keys, a stance critiqued by experts for understating protocol-level risks in secure messaging standards.

Metadata Handling and Jurisdiction

Threema minimizes metadata collection to the extent technically feasible, generating only transient necessary for delivery and deleting it immediately thereafter. Servers maintain no logs linking user IDs or recording communication partners, groups, or timestamps beyond delivery confirmation, ensuring that the platform cannot reconstruct contact networks or interaction histories. This decentralized architecture avoids central storage of , with contact lists and group memberships handled locally on user devices rather than uploaded to servers. Users operate via a randomly generated 8-digit Threema ID, requiring no phone number, , or other identifiers, though optional linking to such details is hashed and used temporarily if provided. IP addresses are logged for 10 days solely for prevention and deleted afterward, while no behavioral or user profiling occurs from metadata. Independent analyses, such as a 2023 Security paper, confirm Threema's metadata restraint aligns with its privacy claims, though they note potential for device-level leaks if users enable optional features like contact synchronization. As a Swiss entity headquartered in Pfäffikon SZ, Threema operates under the Swiss Federal Act on Data Protection (FADP), which mandates strict data minimization and user rights without the expansive surveillance mandates found in U.S. or some frameworks. Servers are hosted exclusively in two ISO 27001-certified data centers in , , precluding foreign over core operations. For /EEA users, GDPR compliance supplements FADP, but Swiss law governs primary processing. This jurisdiction has enabled resistance to overreach; in May 2021, the Swiss Federal Supreme Court ruled against compelled disclosure of user data to law enforcement absent , affirming Threema's non-cooperation with broad requests. Switzerland's neutrality and robust privacy standards prompted the to mandate Threema over in 2022, citing concerns with U.S.-based apps' exposure to entities like the NSA. Threema reports zero successful foreign data handovers, attributing this to limited retained data and Swiss legal barriers.

Identified Vulnerabilities and Fixes

In January 2023, researchers from published an analysis identifying seven cryptographic vulnerabilities in Threema's protocols, presented at the USENIX Security Symposium. These flaws spanned three threat models: passive network attacks allowing message reordering and selective decryption; active network attacks exploiting nonce reuse for message forgery; compromised server scenarios enabling replay or reflection of messages to users without nonce databases (e.g., after app reinstallation); and compelled access attacks recovering private keys from backups via a compression oracle in the Zip4j library (assigned CVE-2023-22899). The researchers emphasized that Threema's custom protocol deviated from cryptographic standards, such as lacking mandatory metadata boxes and relying on optional nonce , which facilitated these issues. Threema acknowledged the disclosure, which occurred responsibly on , 2022, and stated that all vulnerabilities were patched by January 2023 without evidence of real-world exploitation. Key fixes included mandating metadata boxes to prevent reordering and replay attacks, enhancing nonce management to mitigate forgery risks, and updating backup encryption to address the Zip4j oracle vulnerability by improving MAC verification during decryption. Threema introduced the protocol update to enforce these protections, rendering prior attacks infeasible in updated versions. The company commissioned prior independent audits (e.g., by Cure53 in and 2020), which did not uncover these specific protocol flaws, highlighting the value of ongoing external . A public dispute arose when Threema downplayed the flaws' severity, claiming some targeted an outdated protocol and lacked practical impact, prompting researcher rebuttals that the issues affected current implementations and underscored broader lessons in secure design. No subsequent major vulnerabilities have been publicly disclosed as of October 2025, with Threema maintaining open-source code for community verification and continuing periodic audits.

Threema Work

Threema Work is the enterprise-oriented variant of the Threema messaging application, designed to enable secure, privacy-compliant communication within organizations. It extends the consumer version's capabilities with administrative tools for user oversight, policy enforcement, and integration with enterprise systems, while maintaining for all interactions. This setup supports , voice and video calls, group chats, polls, and of various formats, including PDFs and Office documents, across mobile, desktop, and web clients. Administrators access a centralized management cockpit to handle user provisioning, group and broadcast list management, and contact controls, with support for mobile device management (MDM) systems and API integrations for automation, such as Active Directory synchronization. Upcoming add-ons include EasyConnect for QR-code-based external messaging and Circles for granular visibility controls among users. Unlike the consumer app, Threema Work enforces separation of personal and professional communications, offers enhanced compliance reporting, and provides options for on-premises deployment to retain data sovereignty. Security features encompass with perfect , a zero-knowledge that prevents server-side access to message contents, and regular independent security audits. Data is processed and stored exclusively on ISO 27001-certified servers in , adhering to stringent Swiss privacy laws and the European Union's (GDPR), without mandating phone numbers or email addresses for user identification. This jurisdiction avoids data-sharing obligations under laws like the U.S. , prioritizing user anonymity and minimal metadata collection. Pricing follows annual subscription models per user: the Core plan costs €3.00 monthly and includes fundamental secure messaging with central user management; the Professional plan at €5.00 adds advanced administrative options like automated workflows and one-to-many ; the OnPrem variant, priced on request, allows self-hosting for full control. A 30-day free trial is available for up to 30 users. As of recent reports, Threema Work serves over 8,000 organizations globally, emphasizing its adoption for confidential business operations.

Specialized Services (Gateway, OnPrem, etc.)

Threema Gateway enables organizations to integrate Threema messaging into their existing software applications through a dedicated , facilitating automated sending and receiving of messages to Threema users. Launched in March 2015, the service supports text messages up to 3,500 characters, images, files of any type, and custom IDs with profile pictures for specialized use cases such as two-factor , integrations, IoT notifications, and chatbots. It operates via requests to the Gateway server, with options for basic or , and requires no mobile network coverage, relying instead on connectivity. Compared to gateways, it offers superior through asymmetric and verifiable open-source protocols, lower costs with per-message pricing starting at CHF 0.01 and no recurring fees, and greater reliability without carrier dependencies. Threema OnPrem is a self-hosted variant of the Threema platform designed for organizations prioritizing data sovereignty and operational independence from cloud providers. It deploys on customer-owned servers, eliminating data transmission to external parties and ensuring compliance with Swiss data protection standards and GDPR requirements through end-to-end encryption and a zero-knowledge proof architecture. Core functionalities mirror the standard app, including one-on-one and group chats, voice and video calls, file sharing, and polls, alongside administrative features like user lifecycle management, MDM integration, and BYOD policies via a dedicated portal. Unlike the SaaS-based Threema Work, OnPrem maintains a closed, network-independent system with no central metadata storage, reducing exposure to cyber threats and enabling customization through add-ons such as whitelabeling. Deployment supports cross-platform access on mobile and desktop devices, with licensing tied to self-managed infrastructure rather than subscriptions.

Reception and Critiques

Adoption Metrics and User Base

Threema maintains a global user base exceeding 12 million individuals, with over 8,000 business customers utilizing its services as of 2025. This figure encompasses active and registered users across its and enterprise variants, reflecting steady adoption driven by its emphasis on metadata minimization and Swiss . The platform's paid, one-time subscription model—priced at approximately CHF 4 per user—contrasts with ad-supported competitors, resulting in a self-selected cohort prioritizing over free access. User growth originated modestly upon launch in 2012 but surged post-2013 following heightened public awareness of via Edward Snowden's disclosures, expanding to 250,000 users within months. By mid-2021, the base had reached over 10 million, including notable institutional uptake such as the Swiss federal government, , and German Chancellor . Subsequent increments to 11–12 million by 2022–2025 indicate moderated expansion, concentrated in German-speaking where regional surveys highlight Threema's prominence among secure messengers in .
MilestoneApproximate UsersDate/Context
Initial Surge250,0002013 (post-Snowden awareness)
Mid-Growth10 million+May 2021 (consumer base)
Recent Total12 million+ (individuals); 8,000+ businesses2025 (global)
Adoption metrics underscore Threema's niche positioning: while total downloads exceed 60 million across app stores, active engagement remains tied to its core demographics in privacy-sensitive sectors, with limited penetration in English-speaking markets due to network effects favoring larger platforms. Enterprise deployments, via Threema Work, account for millions of additional licenses across thousands of organizations, emphasizing B2B scalability over mass consumer appeal.

Expert Evaluations and Comparisons

Security experts have conducted multiple independent audits of Threema, affirming its robust implementation in several areas while identifying protocol-specific issues. A 2019 audit by Cure53 examined Threema's Android and applications as well as Threema , uncovering no high-risk or critical vulnerabilities, though it recommended enhancements for minor issues like input validation and session management. Threema commissions regular third-party audits by firms such as Cure53 to verify (E2EE) and overall architecture, with apps being open-source to enable community scrutiny. Cryptographic analyses have revealed limitations in Threema's proprietary NaCl-based protocol. In January 2023, researchers from published a detailed identifying seven vulnerabilities, including key reuse risks, nonce predictability, and malleability issues that could enable message forgery or decryption under specific conditions, though none allowed mass compromise without targeted access. Threema developers patched these flaws promptly, updating the protocol to mitigate risks like invalid curve attacks and improving , as confirmed in subsequent statements. Experts such as have highlighted the analysis's value in exposing implementation gaps, emphasizing that while Threema's design prioritizes minimalism, its closed-source cryptographic libraries—unlike fully open alternatives—limit broader verification. In comparisons to peers, Threema is frequently evaluated as superior in and metadata minimization, requiring no phone number or for registration and storing minimal server-side under Swiss , which avoids U.S. or EU mandates. Relative to Signal, experts at and Brosix note Threema's edge in user and decentralized identity (via Threema IDs) but critique its protocol as less mature than Signal's open-source Double Ratchet, which benefits from widespread adoption in apps like and extensive . Signal is deemed more resilient against nation-state threats due to its battle-tested ecosystem, per privacy researchers, though Threema's paid model reduces spam and incentivizes sustainability without ad-driven harvesting. Against , Threema outperforms in by eschewing metadata of contacts and timestamps, which retains despite E2EE, enabling potential network analysis; Versus.com and CyberInsider evaluations quantify this via features like two-way opt-in contacts and anonymous usage. In expert rankings from Molfar Institute and , Threema scores highly (e.g., top-tier for E2EE defaults and no-data policy) but trails Signal overall due to smaller peer-reviewed base and past vulnerabilities, with analysts recommending it for users prioritizing over protocol ubiquity. These assessments underscore Threema's strengths in causal controls—limiting identifiable information at the source—but highlight the need for ongoing open-sourcing of core crypto to match Signal's transparency.

Controversies and Debates

In January 2023, researchers from published an analysis of Threema's cryptographic protocols, identifying seven vulnerabilities that could potentially compromise message integrity and confidentiality under specific conditions, such as cross-protocol attacks and insufficient protection against key compromise in group chats. The study, presented at the USENIX Security Symposium, highlighted issues including the absence of in certain modes and risks from Threema's custom NaCl-based interacting poorly with standard libraries, recommending greater reliance on audited primitives like those in Signal's protocol. These flaws were responsibly disclosed to Threema in October 2022, with fixes implemented before public revelation, and no evidence of real-world exploitation emerged. Threema's developers contested the severity of the findings in a January 9, 2023, statement, arguing that the reported issues were either theoretical, already mitigated by design choices like per-message keys, or misrepresentations of their security model, which prioritizes without centralized metadata storage. This response drew criticism from the research team and security experts, who accused Threema of downplaying legitimate risks and lacking transparency, potentially eroding user trust in implementations over fully open-source alternatives like Signal. The episode fueled broader debates on the adequacy of proactive, independent audits for closed-source elements in Threema's codebase, despite its open protocol specifications, with critics noting that partial openness hinders comprehensive verification. Additional critiques have centered on Threema's marketing practices, including comparisons to competitors that some cryptographers view as misleading, such as emphasizing Signal's U.S. while understating Threema's own reliance on custom crypto that deviates from established standards. In Swiss government contexts, where Threema is used for official communications, the 2023 analysis raised questions about rigor, as the app's flaws predated fixes and highlighted tensions between convenience and verifiable . Proponents counter that Threema's Swiss base offers stronger data protection under non-U.S. laws and minimal metadata collection, positioning it as a viable alternative amid concerns, though adoption remains limited by its paid model and smaller network effects compared to free apps.

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