211 lines
6.6 KiB
C
211 lines
6.6 KiB
C
#include <stdint.h>
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#include <string.h>
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#include "sha-256.h"
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#define CHUNK_SIZE 64
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#define TOTAL_LEN_LEN 8
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/*
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* ABOUT bool: this file does not use bool in order to be as pre-C99 compatible as possible.
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*/
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/*
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* Comments from pseudo-code at https://en.wikipedia.org/wiki/SHA-2 are reproduced here.
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* When useful for clarification, portions of the pseudo-code are reproduced here too.
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*/
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/*
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* Initialize array of round constants:
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* (first 32 bits of the fractional parts of the cube roots of the first 64 primes 2..311):
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*/
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static const uint32_t k[] = {
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0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
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0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
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0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
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0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
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0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
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0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
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0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
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0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
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};
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struct buffer_state {
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const uint8_t * p;
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size_t len;
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size_t total_len;
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int single_one_delivered; // bool
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int total_len_delivered; // bool
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};
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static inline uint32_t right_rot(uint32_t value, unsigned int count)
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{
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/*
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* Defined behaviour in standard C for all count where 0 < count < 32,
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* which is what we need here.
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*/
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return value >> count | value << (32 - count);
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}
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static void init_buf_state(struct buffer_state * state, const void * input, size_t len)
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{
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state->p = input;
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state->len = len;
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state->total_len = len;
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state->single_one_delivered = 0;
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state->total_len_delivered = 0;
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}
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/* Return value: bool */
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static int calc_chunk(uint8_t chunk[CHUNK_SIZE], struct buffer_state * state)
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{
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size_t space_in_chunk;
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if (state->total_len_delivered) {
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return 0;
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}
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if (state->len >= CHUNK_SIZE) {
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memcpy(chunk, state->p, CHUNK_SIZE);
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state->p += CHUNK_SIZE;
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state->len -= CHUNK_SIZE;
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return 1;
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}
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memcpy(chunk, state->p, state->len);
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chunk += state->len;
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space_in_chunk = CHUNK_SIZE - state->len;
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state->p += state->len;
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state->len = 0;
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/* If we are here, space_in_chunk is one at minimum. */
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if (!state->single_one_delivered) {
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*chunk++ = 0x80;
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space_in_chunk -= 1;
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state->single_one_delivered = 1;
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}
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/*
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* Now:
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* - either there is enough space left for the total length, and we can conclude,
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* - or there is too little space left, and we have to pad the rest of this chunk with zeroes.
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* In the latter case, we will conclude at the next invokation of this function.
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*/
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if (space_in_chunk >= TOTAL_LEN_LEN) {
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const size_t left = space_in_chunk - TOTAL_LEN_LEN;
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size_t len = state->total_len;
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int i;
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memset(chunk, 0x00, left);
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chunk += left;
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/* Storing of len * 8 as a big endian 64-bit without overflow. */
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chunk[7] = (uint8_t) (len << 3);
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len >>= 5;
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for (i = 6; i >= 0; i--) {
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chunk[i] = (uint8_t) len;
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len >>= 8;
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}
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state->total_len_delivered = 1;
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} else {
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memset(chunk, 0x00, space_in_chunk);
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}
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return 1;
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}
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/*
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* Limitations:
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* - Since input is a pointer in RAM, the data to hash should be in RAM, which could be a problem
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* for large data sizes.
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* - SHA algorithms theoretically operate on bit strings. However, this implementation has no support
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* for bit string lengths that are not multiples of eight, and it really operates on arrays of bytes.
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* In particular, the len parameter is a number of bytes.
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*/
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void calc_sha_256(uint8_t hash[32], const void * input, size_t len)
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{
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/*
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* Note 1: All integers (expect indexes) are 32-bit unsigned integers and addition is calculated modulo 2^32.
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* Note 2: For each round, there is one round constant k[i] and one entry in the message schedule array w[i], 0 = i = 63
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* Note 3: The compression function uses 8 working variables, a through h
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* Note 4: Big-endian convention is used when expressing the constants in this pseudocode,
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* and when parsing message block data from bytes to words, for example,
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* the first word of the input message "abc" after padding is 0x61626380
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*/
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/*
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* Initialize hash values:
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* (first 32 bits of the fractional parts of the square roots of the first 8 primes 2..19):
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*/
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uint32_t h[] = { 0x6a09e667, 0xbb67ae85, 0x3c6ef372, 0xa54ff53a, 0x510e527f, 0x9b05688c, 0x1f83d9ab, 0x5be0cd19 };
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int i, j;
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/* 512-bit chunks is what we will operate on. */
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uint8_t chunk[64];
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struct buffer_state state;
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init_buf_state(&state, input, len);
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while (calc_chunk(chunk, &state)) {
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uint32_t ah[8];
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/*
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* create a 64-entry message schedule array w[0..63] of 32-bit words
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* (The initial values in w[0..63] don't matter, so many implementations zero them here)
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* copy chunk into first 16 words w[0..15] of the message schedule array
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*/
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uint32_t w[64];
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const uint8_t *p = chunk;
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memset(w, 0x00, sizeof w);
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for (i = 0; i < 16; i++) {
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w[i] = (uint32_t) p[0] << 24 | (uint32_t) p[1] << 16 |
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(uint32_t) p[2] << 8 | (uint32_t) p[3];
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p += 4;
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}
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/* Extend the first 16 words into the remaining 48 words w[16..63] of the message schedule array: */
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for (i = 16; i < 64; i++) {
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const uint32_t s0 = right_rot(w[i - 15], 7) ^ right_rot(w[i - 15], 18) ^ (w[i - 15] >> 3);
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const uint32_t s1 = right_rot(w[i - 2], 17) ^ right_rot(w[i - 2], 19) ^ (w[i - 2] >> 10);
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w[i] = w[i - 16] + s0 + w[i - 7] + s1;
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}
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/* Initialize working variables to current hash value: */
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for (i = 0; i < 8; i++)
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ah[i] = h[i];
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/* Compression function main loop: */
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for (i = 0; i < 64; i++) {
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const uint32_t s1 = right_rot(ah[4], 6) ^ right_rot(ah[4], 11) ^ right_rot(ah[4], 25);
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const uint32_t ch = (ah[4] & ah[5]) ^ (~ah[4] & ah[6]);
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const uint32_t temp1 = ah[7] + s1 + ch + k[i] + w[i];
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const uint32_t s0 = right_rot(ah[0], 2) ^ right_rot(ah[0], 13) ^ right_rot(ah[0], 22);
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const uint32_t maj = (ah[0] & ah[1]) ^ (ah[0] & ah[2]) ^ (ah[1] & ah[2]);
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const uint32_t temp2 = s0 + maj;
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ah[7] = ah[6];
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ah[6] = ah[5];
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ah[5] = ah[4];
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ah[4] = ah[3] + temp1;
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ah[3] = ah[2];
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ah[2] = ah[1];
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ah[1] = ah[0];
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ah[0] = temp1 + temp2;
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}
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/* Add the compressed chunk to the current hash value: */
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for (i = 0; i < 8; i++)
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h[i] += ah[i];
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}
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/* Produce the final hash value (big-endian): */
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for (i = 0, j = 0; i < 8; i++)
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{
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hash[j++] = (uint8_t) (h[i] >> 24);
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hash[j++] = (uint8_t) (h[i] >> 16);
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hash[j++] = (uint8_t) (h[i] >> 8);
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hash[j++] = (uint8_t) h[i];
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}
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}
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