Fuzzy extractors are a method that allows biometric data to be used as inputs to standard cryptographic techniques, to enhance computer security. "Fuzzy", in this context, refers to the fact that the fixed values required for cryptography will be extracted from values close to but not identical to the original key, without compromising the security required. One application is to encrypt and authenticate users records, using the biometric inputs of the user as a key.

Fuzzy extractors are a biometric tool that allows for user authentication, using a biometric template constructed from the user's biometric data as the key, by extracting a uniform and random string ${\displaystyle R}$ from an input ${\displaystyle w}$, with a tolerance for noise. If the input changes to ${\displaystyle w'}$ but is still close to ${\displaystyle w}$, the same string ${\displaystyle R}$ will be re-constructed. To achieve this, during the initial computation of ${\displaystyle R}$ the process also outputs a helper string ${\displaystyle P}$ which will be stored to recover ${\displaystyle R}$ later and can be made public without compromising the security of ${\displaystyle R}$. The security of the process is also ensured when an adversary modifies ${\displaystyle P}$. Once the fixed string ${\displaystyle R}$ has been calculated, it can be used, for example, for key agreement between a user and a server based only on a biometric input.

One precursor to fuzzy extractors was the so-called "Fuzzy Commitment", as designed by Juels and Wattenberg. Here, the cryptographic key is decommitted using biometric data.

Later, Juels and Sudan came up with Fuzzy vault schemes. These are order invariant for the fuzzy commitment scheme and use a Reed–Solomon error correction code. The code word is inserted as the coefficients of a polynomial, and this polynomial is then evaluated with respect to various properties of the biometric data.

Both Fuzzy Commitment and Fuzzy Vaults were precursors to Fuzzy Extractors.^{[citation needed]}

In order for fuzzy extractors to generate strong keys from biometric and other noisy data, cryptography paradigms will be applied to this biometric data. These paradigms:

(1) Limit the number of assumptions about the content of the biometric data (this data comes from a variety of sources; so, in order to avoid exploitation by an adversary, it's best to assume the input is unpredictable).

(2) Apply usual cryptographic techniques to the input. (Fuzzy extractors convert biometric data into secret, uniformly random, and reliably reproducible random strings.)