laantungir/otp
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases 35 Wiki Activity

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

Browse Source
This commit is contained in:
Laan Tungir
2025-12-24 10:00:27 -05:00
parent 2c311a9a61
commit 977da58a3b
5 changed files with 366 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

40
src/entropy.c
View File

@@ -219,8 +219,22 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
unsigned char buffer[64 * 1024]; // 64KB chunks
unsigned char keystream[64 * 1024];
uint64_t offset = 0;
uint32_t counter = 0;
uint32_t counter_low = 0;
uint32_t counter_high = 0;
time_t start_time = time(NULL);
// Use extended counter for pads larger than 256GB
// 256GB = 2^32 blocks * 64 bytes = 274,877,906,944 bytes
int use_extended = (pad_size > 274877906944ULL);
// For extended mode, use reduced 8-byte nonce
unsigned char nonce_reduced[8];
if (use_extended) {
memcpy(nonce_reduced, nonce + 4, 8);
if (display_progress) {
printf("Using extended counter mode for large pad (>256GB)\n");
}
}
while (offset < pad_size) {
size_t chunk_size = sizeof(buffer);
@@ -237,7 +251,15 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
}
// Generate keystream for this chunk
if (chacha20_encrypt(key, counter, nonce, buffer, keystream, chunk_size) != 0) {
int chacha_result;
if (use_extended) {
chacha_result = chacha20_encrypt_extended(key, counter_low, counter_high,
nonce_reduced, buffer, keystream, chunk_size);
} else {
chacha_result = chacha20_encrypt(key, counter_low, nonce, buffer, keystream, chunk_size);
}
if (chacha_result != 0) {
printf("Error: Chacha20 keystream generation failed\n");
fclose(pad_file);
chmod(pad_path, S_IRUSR);
@@ -265,7 +287,16 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
}
offset += chunk_size;
counter += (chunk_size + 63) / 64; // Round up for block count
// Update counters
uint32_t blocks = (chunk_size + 63) / 64; // Round up for block count
uint32_t old_counter_low = counter_low;
counter_low += blocks;
// Check for overflow and increment high counter
if (counter_low < old_counter_low) {
counter_high++;
}
// Show progress for large pads
if (display_progress && offset % (64 * 1024 * 1024) == 0) { // Every 64MB
@@ -282,7 +313,8 @@ int add_entropy_chacha20(const char* pad_chksum, const unsigned char* entropy_da
if (display_progress) {
show_progress(pad_size, pad_size, start_time);
printf("\n✓ Entropy successfully added to pad using Chacha20\n");
printf("\n✓ Entropy successfully added to pad using Chacha20%s\n",
use_extended ? " (extended counter)" : "");
printf("✓ Pad integrity maintained\n");
printf("✓ %zu bytes of entropy distributed across entire pad\n", entropy_size);
printf("✓ Pad restored to read-only mode\n");

46
src/nostr_chacha20.c
View File

@@ -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;
}

27
src/nostr_chacha20.h
View File

@@ -63,10 +63,10 @@ int chacha20_block(const uint8_t key[32], uint32_t counter,
/**
* ChaCha20 encryption/decryption
*
*
* Encrypts or decrypts data using ChaCha20 stream cipher.
* Since ChaCha20 is a stream cipher, encryption and decryption are the same operation.
*
*
* @param key[in] 32-byte key
* @param counter[in] Initial 32-bit counter value
* @param nonce[in] 12-byte nonce
@@ -75,10 +75,29 @@ int chacha20_block(const uint8_t key[32], uint32_t counter,
* @param length[in] Length of input data in bytes
* @return 0 on success, negative on error
*/
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);
/**
* ChaCha20 encryption/decryption with extended counter (64-bit)
*
* Extended version that supports files larger than 256GB by using
* part of the nonce as a high-order counter extension.
*
* @param key[in] 32-byte key
* @param counter_low[in] Initial 32-bit counter value (low bits)
* @param counter_high[in] Initial 32-bit counter value (high bits)
* @param nonce[in] 8-byte reduced nonce (instead of 12)
* @param input[in] Input data to encrypt/decrypt
* @param output[out] Output buffer (can be same as input)
* @param length[in] Length of input data in bytes
* @return 0 on success, negative on error
*/
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);
/*
* ============================================================================
* UTILITY FUNCTIONS