Keccak: Hash and encryption

Keccak is the crypto primitive for SHA-3, and can be used as hash as well as pseudo random number generator or as authenticated encryption/decryption.

Keccak uses 64 bits by default, a 32 bit version will follow.

User functions

Crypto primitives

• st0 ( -- ) clear state
• keccakf ( -- ) the diffusion function
• >sponge ( addr u -- ) Absorb string into state (string must be cell-sized)
• >duplex ( addr u -- ) Absorb and encrypt string
• duplex> ( addr u -- ) Absorb and decrypt string
• padded ( addr1 u1 u2 -- addr2 u2 ) Pad string

Usage examples

• hash256 ( addr u -- ) compute a 256 bit hash (not identical to sha-3)

  : hash256 ( addr u -- )
    st0  bounds ?DO
        I I' over - $88 umin
        dup $88 u< IF $88 padded  THEN  >sponge
        keccakf
    $88 +LOOP ;
  

• end256 ( addr u1 key u2 -- ) encode message with key

  : enc256 ( addr u1 key u2 -- )
    st0 >sponge keccakf
    bounds ?DO
        I I' over - $88 umin
        dup $88 u< IF
            2dup $88 padded >duplex
            kpad -rot move
        ELSE  >duplex  THEN
        keccakf
    $88 +LOOP ;
  

• dec256 ( addr u1 key u2 -- ) decode message with key

  : dec256 ( addr u1 key u2 -- )
    st0 >sponge keccakf
    bounds ?DO
        I I' over - $88 umin
        dup $88 u< IF
            2dup $88 padded >duplex
            kpad -rot move
        ELSE  >duplex  THEN
        keccakf
    $88 +LOOP ;