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keccak: Rework absorption of the final input bytes #1620

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Merged
chfast merged 1 commit into from
Aug 9, 2026
Merged

keccak: Rework absorption of the final input bytes #1620

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27 changes: 9 additions & 18 deletions lib/evmone_precompiles/keccak.c
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Original file line number Diff line number Diff line change
Expand Up @@ -323,16 +323,11 @@ static inline ALWAYS_INLINE void keccak(
const size_t hash_size = bits / 8;
const size_t block_size = (1600 - bits * 2) / 8;

size_t i;
uint64_t* state_iter;
uint64_t last_word = 0;
uint8_t* last_word_iter = (uint8_t*)&last_word;

uint64_t state[25] = {0};

while (size >= block_size)
{
for (i = 0; i < (block_size / word_size); ++i)
for (size_t i = 0; i < (block_size / word_size); ++i)
{
state[i] ^= load_le(data);
data += word_size;
Expand All @@ -343,7 +338,7 @@ static inline ALWAYS_INLINE void keccak(
size -= block_size;
}

state_iter = state;
uint64_t* state_iter = state;

while (size >= word_size)
{
Expand All @@ -353,21 +348,17 @@ static inline ALWAYS_INLINE void keccak(
size -= word_size;
}

while (size > 0)
{
*last_word_iter = *data;
++last_word_iter;
++data;
--size;
}
*last_word_iter = 0x01;
*state_iter ^= to_le64(last_word);
// Absorb last 0–7 bytes of input + the padding byte.
uint64_t last_word = (uint64_t)0x01 << (size * 8);
for (size_t i = 0; i < size; ++i)
last_word |= (uint64_t)data[i] << (i * 8);
*state_iter ^= last_word;

state[(block_size / word_size) - 1] ^= 0x8000000000000000;
state[(block_size / word_size) - 1] ^= 0x8000000000000000; // Last block bit flip.

keccakf1600_best(state);

for (i = 0; i < (hash_size / word_size); ++i)
for (size_t i = 0; i < (hash_size / word_size); ++i)
out[i] = to_le64(state[i]);
}

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