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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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40
src/entropy.c
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@@ -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");