3 ms·
Not quite. A key derivation function needs to have a lot of the same properties as a pseudorandom function (which is the space cryptographic hash functions occ
by some_furry 5y ago
Not quite.
A key derivation function needs to have a lot of the same properties as a pseudorandom function (which is the space cryptographic hash functions occupy), but with additional requirements.
1. It needs a secret input. This is the password (for Password KDFs) or Initial Key Material. Cryptographic hash functions do not.
2. It needs to satisfy a stronger security model. See section 3 of this paper, especially definition 7: https://eprint.iacr.org/2010/264.pdf https://eprint.iacr.org/2010/264.pdf
There's some overlap (Argon2id, scrypt) between PHFs and KDFs. There's exclusion in both categories. Bcrypt is a PHF, not a KDF. HKDF is a KDF, not a PHF.