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Computes the Keccak-256 hash of a byte sequence with custom padding. This function allows hashing arbitrary byte sequences by providing the input as 64-bit words in little-endian format and a final partial word.

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Signature

pub fn cairo_keccak(ref input: Array, last_input_word: u64, last_input_num_bytes: u32) -> u256

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Arguments

  • input - Array of complete 64-bit words in little-endian format
  • last_input_word - Final partial word (if any)
  • last_input_num_bytes - Number of valid bytes in the final word (0-7)

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Returns

The 32-byte Keccak-256 hash as a little-endian u256

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Panics

Panics if last_input_num_bytes is greater than 7.

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Examples

use core::keccak::cairo_keccak;

// Hash "Hello world!" by splitting into 64-bit words in little-endian
let mut input = array![0x6f77206f6c6c6548]; // a full 8-byte word
let hash = cairo_keccak(ref input, 0x21646c72, 4); // 4 bytes of the last word
assert!(hash == 0xabea1f2503529a21734e2077c8b584d7bee3f45550c2d2f12a198ea908e1d0ec);