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using rolling-hash-like way to count why2_sum_segment

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This commit is contained in:
Václav Šmejkal 2024-11-20 16:32:13 +01:00
parent b50305f080
commit 10fe26cca1
Signed by: ENGO150
GPG Key ID: 4A57E86482968843
2 changed files with 8 additions and 8 deletions
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3
include/crypto.h
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@ -24,8 +24,7 @@ extern "C" {
#endif #endif
//MACROS //MACROS
#define WHY2_CHECKSUM_SEGMENT_SIZE 32 //SEGMENT SIZE FOR CALCULATING SUM #define WHY2_SUM_SEGMENT_SIZE 32 //SEGMENT SIZE FOR CALCULATING SUM
#define WHY2_CHECKSUM_PRIME 11 //PRIME NUMBER FOR ROTATION
#define WHY2_SUM_BASE_PRIME 31 //PRIME FOR SUM BASE #define WHY2_SUM_BASE_PRIME 31 //PRIME FOR SUM BASE
#define WHY2_SUM_MOD_PRIME 4294967295UL //PRIME FOR SUM MODULUS #define WHY2_SUM_MOD_PRIME 4294967295UL //PRIME FOR SUM MODULUS

13
src/core/lib/utils/crypto.c
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@ -24,18 +24,19 @@ along with this program. If not, see <https://www.gnu.org/licenses/>.
unsigned long why2_sum_segment(char *input) //I ABSOLUTELY DO NOT RECOMMEND USING THIS WITH LARGE KEYS!!! unsigned long why2_sum_segment(char *input) //I ABSOLUTELY DO NOT RECOMMEND USING THIS WITH LARGE KEYS!!!
{ {
unsigned long input_size = strlen(input); unsigned long input_size = strlen(input);
unsigned long segmented_input_size = ceil(input_size / (double) WHY2_CHECKSUM_SEGMENT_SIZE) * WHY2_CHECKSUM_SEGMENT_SIZE; //CALCULATE CLOSEST 4*n TO input unsigned long segmented_input_size = ceil(input_size / (double) WHY2_SUM_SEGMENT_SIZE) * WHY2_SUM_SEGMENT_SIZE; //CALCULATE CLOSEST 32*n (OR WHY2_SUM_SEGMENT_SIZE*n, IF YOU WILL) TO input
unsigned long output = 0; unsigned long output = 0;
for (unsigned long i = 0; i < segmented_input_size / WHY2_CHECKSUM_SEGMENT_SIZE; i++) //DIVIDE buffer INTO SEGMENTS, XOR EACH OTHER AND ADD TO output for (unsigned long i = 0; i < segmented_input_size / WHY2_SUM_SEGMENT_SIZE; i++) //DIVIDE buffer INTO SEGMENTS, XOR EACH OTHER AND ADD TO output
{ {
unsigned long output_buffer = 0; unsigned long output_buffer = 0;
for (unsigned long j = 0; j < WHY2_CHECKSUM_SEGMENT_SIZE; j++) for (unsigned long j = 0; j < WHY2_SUM_SEGMENT_SIZE; j++)
{ {
unsigned long index_buffer = i * WHY2_CHECKSUM_SEGMENT_SIZE + j; unsigned long index_buffer = i * WHY2_SUM_SEGMENT_SIZE + j;
char value_buffer = (input_size > index_buffer) ? input[index_buffer] : 0;
output_buffer ^= (input_size > index_buffer) ? input[index_buffer] : 0; //XORING output_buffer ^= value_buffer; //XORING
output_buffer = (output_buffer << WHY2_CHECKSUM_PRIME) | (output_buffer >> (sizeof(unsigned long) * 8 - WHY2_CHECKSUM_PRIME)); //ROTATE output_buffer = (output_buffer * WHY2_SUM_BASE_PRIME + value_buffer) % WHY2_SUM_MOD_PRIME;
} }
output += output_buffer; //ADD output += output_buffer; //ADD