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Version v0.3.37 - Implement ChaCha20 nonce extension to support pads larger than 256GB

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Laan Tungir
2025-12-24 10:00:27 -05:00
parent 2c311a9a61
commit 977da58a3b
5 changed files with 366 additions and 10 deletions
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46
src/nostr_chacha20.c
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@@ -129,8 +129,8 @@ int chacha20_block(const uint8_t key[32], uint32_t counter,
return 0;
}
int chacha20_encrypt(const uint8_t key[32], uint32_t counter,
const uint8_t nonce[12], const uint8_t* input,
int chacha20_encrypt(const uint8_t key[32], uint32_t counter,
const uint8_t nonce[12], const uint8_t* input,
uint8_t* output, size_t length) {
uint8_t keystream[CHACHA20_BLOCK_SIZE];
size_t offset = 0;
@@ -161,3 +161,45 @@ int chacha20_encrypt(const uint8_t key[32], uint32_t counter,
return 0;
}
int chacha20_encrypt_extended(const uint8_t key[32], uint32_t counter_low,
uint32_t counter_high, const uint8_t nonce[8],
const uint8_t* input, uint8_t* output, size_t length) {
uint8_t keystream[CHACHA20_BLOCK_SIZE];
uint8_t extended_nonce[12];
size_t offset = 0;
while (length > 0) {
/* Build extended 12-byte nonce: [counter_high (4 bytes)][nonce (8 bytes)] */
u32_to_bytes_le(counter_high, extended_nonce);
memcpy(extended_nonce + 4, nonce, 8);
/* Generate keystream block using extended nonce */
int ret = chacha20_block(key, counter_low, extended_nonce, keystream);
if (ret != 0) {
return ret;
}
/* XOR with input to produce output */
size_t block_len = (length < CHACHA20_BLOCK_SIZE) ? length : CHACHA20_BLOCK_SIZE;
for (size_t i = 0; i < block_len; i++) {
output[offset + i] = input[offset + i] ^ keystream[i];
}
/* Move to next block */
offset += block_len;
length -= block_len;
counter_low++;
/* Check for counter_low overflow and increment counter_high */
if (counter_low == 0) {
counter_high++;
/* Check for counter_high overflow (extremely unlikely - > 1 exabyte) */
if (counter_high == 0) {
return -1; /* Extended counter wrapped around */
}
}
}
return 0;
}