Cloudera Docs

Scrypt

  • This KDF was added in v0.5.0.

  • https://en.wikipedia.org/wiki/Scrypt is an adaptive function designed in response to bcrypt. This KDF is recommended as it requires relatively large amounts of memory for each derivation, making it resistant to hardware brute-force attacks.

  • The recommended minimum cost is N=214 (16,384), r=8, p=1 (as of 2/1/2016 on commodity hardware). p must be a positive integer and less than (2^32 − 1) * (Hlen/MFlen) where Hlen is the length in octets of the digest function output (32 for SHA-256) and MFlen is the length in octets of the mixing function output, defined as r * 128. These parameters should be increased to the threshold at which legitimate systems will encounter detrimental delays (see schedule below or use ScryptCipherProviderGroovyTest#testDefaultConstructorShouldProvideStrongParameters() to calculate safe minimums).

  • The salt format is $s0$e0101$ABCDEFGHIJKLMNOPQRSTUV. The salt is delimited by $ and the three sections are as follows:

    • s0 - the version of the format. NiFi currently uses s0 for all salts generated internally.

    • e0101 - the cost parameters. This is actually a hexadecimal encoding of N, r, p using shifts. This can be formed/parsed using Scrypt#encodeParams() and Scrypt#parseParameters().

      • Some external libraries encode N, r, and p separately in the form $4000$1$1$ (N is stored in hex encoding as 0x4000, which is 0d16384, or 214 as 0xe = 0d14). A utility method is available at ScryptCipherProvider#translateSalt() which will convert the external form to the internal form.

    • ABCDEFGHIJKLMNOPQRSTUV - the 12-44 character, Base64-encoded, unpadded, raw salt value. This decodes to a 8-32 byte salt used in the key derivation.