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FIPS202.md

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Replacing FIPS-202

If your library has a FIPS-2021 implementation, you can use it instead of the one shipped with mlkem-native.

  1. Replace mlkem/src/fips202/* by your own FIPS-202 implementation.
  2. Provide replacements for the headers mlkem/src/fips202/fips202.h and mlkem/src/fips202/fips202x4.h and the functionalities specified therein:
  • Structure definitions for mlk_shake128ctx and mlk_shake128x4ctx
  • mlk_shake128_absorb_once(): Initialize a SHAKE-128 context and perform a single absorb step.
  • mlk_shake128_squeezeblocks(): Squeeze SHAKE-128 context
  • mlk_shake128_release(): Release a SHAKE-128 context after use
  • mlk_shake256(), mlk_sha3_256(), mlk_sha3_512(): One-shot SHAKE-256 / SHA3-256 / SHA3-512 operations
  • mlk_shake256x4(): One-shot 4x-batched SHAKE-256 operation
  • mlk_shake128x4_absorb_once(): Initialize a 4x-batched SHAKE-128 context and perform a single absorb step.
  • mlk_shake128x4_squeezeblocks(): Squeeze 4x-batched SHAKE-128 context
  • mlk_shake128x4_release(): Release a 4x-batched SHAKE-128 context after use

See mlkem/src/fips202/fips202.h and mlkem/src/fips202/fips202x4.h for more details. Note that the structure definitions may differ from those shipped with mlkem-native: In particular, you may fall back to an incremental hashing implementation which tracks the current offset in its state.

Example

See examples/bring_your_own_fips202/ for an example how to use a custom FIPS-202 implementation.

Footnotes

  1. National Institute of Standards and Technology: FIPS202 SHA-3 Standard: Permutation-Based Hash and Extendable-Output Functions, https://csrc.nist.gov/pubs/fips/202/final ↩