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Move PBKDF2 to a pwhash category, clarify what that category is 

Password hashing functions are not general-purpose KDFs, and KDFs
don't have to satisfy the same properties as a PHF.

This will allow fast KDFs such as the HKDF construction to be in a
category of their own, while clarifying what functions are suitable
for using passwords as inputs.
master
Frank Denis 2020-09-23 21:37:16 +02:00 committed by Andrew Kelley
parent 72f4cdb2b4
commit c8cd6145ac
1 changed files with 17 additions and 6 deletions
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23
lib/std/crypto.zig
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@ -35,12 +35,23 @@ pub const onetimeauth = struct {
pub const Poly1305 = @import("crypto/poly1305.zig").Poly1305;
};
/// A Key Derivation Function (KDF) is intended to turn a weak, human generated password into a
/// strong key, suitable for cryptographic uses. It does this by salting and stretching the
/// password. Salting injects non-secret random data, so that identical passwords will be converted
/// into unique keys. Stretching applies a deliberately slow hashing function to frustrate
/// brute-force guessing.
pub const kdf = struct {
/// A password hashing function derives a uniform key from low-entropy input material such as passwords.
/// It is intentionally slow or expensive.
///
/// With the standard definition of a key derivation function, if a key space is small, an exhaustive search may be practical.
/// Password hashing functions make exhaustive searches way slower or way more expensive, even when implemented on GPUs and ASICs, by using different, optionally combined strategies:
///
/// - Requiring a lot of computation cycles to complete
/// - Requiring a lot of memory to complete
/// - Requiring multiple CPU cores to complete
/// - Requiring cache-local data to complete in reasonable time
/// - Requiring large static tables
/// - Avoiding precomputations and time/memory tradeoffs
/// - Requiring multi-party computations
/// - Combining the input material with random per-entry data (salts), application-specific contexts and keys
///
/// Password hashing functions must be used whenever sensitive data has to be directly derived from a password.
pub const pwhash = struct {
pub const pbkdf2 = @import("crypto/pbkdf2.zig").pbkdf2;
};