Replacing FIPS-202

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

1. Replace mldsa/src/fips202/* by your own FIPS-202 implementation.
2. Provide replacements for the headers mldsa/src/fips202/fips202.h and mldsa/src/fips202/fips202x4.h and the functionalities specified therein:

• Structure definitions for mld_shake128ctx, mld_shake256ctx, mld_shake128x4ctx, and mld_shake256x4ctx
• mld_shake128_init(): Initialize a SHAKE-128 context
• mld_shake128_absorb(): Absorb data into a SHAKE-128 context (can be called multiple times)
• mld_shake128_finalize(): Finalize the absorb phase of a SHAKE-128 context
• mld_shake128_squeeze(): Squeeze data from a SHAKE-128 context (can be called multiple times)
• mld_shake128_release(): Release and securely zero a SHAKE-128 context after use
• mld_shake256_init(): Initialize a SHAKE-256 context
• mld_shake256_absorb(): Absorb data into a SHAKE-256 context (can be called multiple times)
• mld_shake256_finalize(): Finalize the absorb phase of a SHAKE-256 context
• mld_shake256_squeeze(): Squeeze data from a SHAKE-256 context (can be called multiple times)
• mld_shake256_release(): Release and securely zero a SHAKE-256 context after use
• mld_shake256(): One-shot SHAKE-256 operation
• mld_shake128x4_init(): Initialize a 4x-batched SHAKE-128 context
• mld_shake128x4_absorb_once(): Initialize and absorb into a 4x-batched SHAKE-128 context in one step
• mld_shake128x4_squeezeblocks(): Squeeze blocks from a 4x-batched SHAKE-128 context
• mld_shake128x4_release(): Release a 4x-batched SHAKE-128 context after use
• mld_shake256x4_init(): Initialize a 4x-batched SHAKE-256 context
• mld_shake256x4_absorb_once(): Initialize and absorb into a 4x-batched SHAKE-256 context in one step
• mld_shake256x4_squeezeblocks(): Squeeze blocks from a 4x-batched SHAKE-256 context
• mld_shake256x4_release(): Release a 4x-batched SHAKE-256 context after use

See mldsa/src/fips202/fips202.h and mldsa/src/fips202/fips202x4.h for more details. Note that the structure definitions may differ from those shipped with mldsa-native.

Example

See examples/bring_your_own_fips202/ for an example how to use a custom FIPS-202 implementation with tiny_sha3².

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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 ↩

2. Markku-Juhani O. Saarinen: tiny_sha3, https://github.com/mjosaarinen/tiny_sha3 ↩