SHA-256是一種安全散列(哈希)演算法(Security Hash Algorithm)，它可以將任意長度的輸入資訊轉化成256位長度的哈希數值(也稱作'訊息摘要'或'印鑒')．SHA-256通常用在數字簽名和密碼保護中，比如區塊鏈. 我們可以用生成的哈希數值和原始的哈希數值作對比，這樣不用查驗資訊具體內容即可驗證資訊是否被篡改過．
網路上有很多關于SHA-256演算法原理和基本步驟的文章，我參考了這一篇: https://qvault.io/2020/07/08/how-sha-2-works-step-by-step-sha-256
下面直接貼上代碼和相關注釋：
/*-------------------------------------------------------------------
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License version 2 as
published by the Free Software Foundation.
A test for SHA-256 digesting.
Principle reference:
https://qvault.io/2020/07/08/how-sha-2-works-step-by-step-sha-256
Note:
1. All addition result in modulo of 2^32!
2. Test running system: Little_Endian!
Midas Zhou
https://github.com/widora/wegi
-------------------------------------------------------------------*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
/* 右移運算Right shift */
#define RTSHIFT(x,n) ( (x)>>(n) )
/* 回圈右移Right rotate */
#define RTROT(xsize,x,n) ( ((x)>>(n)) | ( ((x)&((1<<(n+1))-1)) << ( ((xsize)<<3)-(n) )) )
/*----------------
Main()
----------------*/
int main(int argc, char **argv)
{
int i;
unsigned char *input=NULL;
int nk;
uint8_t chunk_data[512/8]={0}; /* 512bits資訊塊 */
unsigned int nch; /* 資訊塊總數 Total number of 512bits_chunks */
unsigned int mod; /* 資訊長度關于512的余數 Result of mod calculation: msgbitlen%512 */
uint32_t words[64]={0}; /* 運算字單元 32*64 = 2048 bits */
unsigned long len; /* length in bytes */
unsigned long bitlen; /* length in bits */
unsigned char digest[8*8+1]={0}; /* convert u32 hv[0-7] to string by sprintf(%08x) */
/* hv_primes[8] 從前８個素數的平方根中提取的哈希初始值 */
static uint32_t hv_primes[8]= {
0x6a09e667,
0xbb67ae85,
0x3c6ef372,
0xa54ff53a,
0x510e527f,
0x9b05688c,
0x1f83d9ab,
0x5be0cd19
};
/* Variable hash values: 哈希值變數 */
uint32_t hv[8];
/* kv_primes[64] 從前６４個素數的立方根中提取的kv初始值 round constants */
const uint32_t kv_primes[64]= {
0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
};
/* Variable round constants kv[64] kV變數 */
uint32_t kv[64];
/* SHA compression vars 運算變數 */
uint32_t a,b,c,d,e,f,g,h;
uint32_t s0, s1, ch, temp1, temp2, maj;
/* 0. 讀取輸入資訊 Get input string */
if(argc>1)
input=(unsigned char *)argv[1];
/* 1. 前處理 Pre-processing */
len=strlen((char *)input);
bitlen=len*8;
/* 計算訊息位長，塊數和余數 bitlen, nch, mod */
mod=bitlen%512;
/* mod > 448-1: fill the last chunk and need a new chunck */
if(mod > 448-1) {
nch=bitlen/512+2;
}
/* mod <= 448-1: fill the last chunk. */
else
nch=bitlen/512+1;
printf("Input message has %lubits, with mod=%d %s 448-1!\n", bitlen, mod, mod>448-1?">":"<=");
/* 2. 初始化哈希值變數 Init hash values hv[8] */
for(i=0; i<8; i++)
hv[i]=hv_primes[i];
/* 3. 初始化kv Init round constants kv[64] */
for(i=0; i<64; i++)
kv[i]=kv_primes[i];
/* ---- 對每個訊息塊進行哈希計算 chunk loop ---- */
for(nk=0; nk<nch; nk++) {
printf("\n\t--- nk=%d ---\n", nk);
/* 4. 分情況加載512位訊息塊 Loak chunck_data[64] */
if( mod <= 448-1 ) {
/* For complete chunck blocks */
if( nk < nch-1 )
memcpy((void *)chunk_data, input+(nk*(512>>3)), (512>>3));
/* The last block, Need to fill 1+0s for the last chunk */
else { /* nk == nch -1 */
bzero(chunk_data, sizeof(chunk_data));
memcpy((void *)chunk_data, input+(nk*(512>>3)), mod>>3);
/* Append a single 1, big_endian */
chunk_data[mod>>3]=0x80;
/* 加入訊息長度 Append 64bits to the end of chunk, as BIT_LENGTH of original message, in big_endian! */
for(i=0; i<sizeof(bitlen); i++)
*(chunk_data+(512>>3)-1-i) = (bitlen>>(i*8))&0xff; /* Big_endian */
}
}
else if( mod > 448-1 ) {
/* For complete chunck blocks */
if( nk < nch-2 )
memcpy((void *)chunk_data, input+(nk*(512>>3)), (512>>3));
/* The last block of original msg, appended with 1+0s to complete a 512bits chunck. */
else if( nk == nch-2 ) {
bzero(chunk_data, sizeof(chunk_data));
memcpy((void *)chunk_data, input+(nk*(512>>3)), mod>>3);
/* Append a single 1, big_endian */
chunk_data[mod>>3]=0x80;
}
/* Additional new chunk, as the last chunck. */
else { /* nk == nch -1 */
/* All 0s */
bzero(chunk_data, sizeof(chunk_data));
/* 加入訊息長度 Append 64bits to the end of chunk, as BIT_LENGTH of original message, in big_endian! */
for(i=0; i<sizeof(bitlen); i++)
*(chunk_data+(512>>3)-1-i) = (bitlen>>(i*8))&0xff; /* Big_endian */
}
}
/* 5. 生成運算字單元 words[64] */
/* 5.1 words[0]~[15]: u8 chunck_data[64] ---> u32 words[64] */
for(i=0; i<16; i++) {
words[i]=(chunk_data[4*i]<<24) +(chunk_data[4*i+1]<<16)+(chunk_data[4*i+2]<<8)+chunk_data[4*i+3];
}
/* 5.2 words[15]~[63]: 48 more words */
for(i=16; i<64; i++) {
/* s0 = (w[i-15] rightrotate 7) xor (w[i-15] rightrotate 18) xor (w[i-15] rightshift 3) */
s0=RTROT(4,words[i-15],7) ^ RTROT(4,words[i-15],18) ^ RTSHIFT(words[i-15],3);
/* s1 = (w[i- 2] rightrotate 17) xor (w[i- 2] rightrotate 19) xor (w[i- 2] rightshift 10) */
s1=RTROT(4,words[i-2],17) ^ RTROT(4,words[i-2],19) ^ RTSHIFT(words[i-2],10);
/* w[i] = w[i-16] + s0 + w[i-7] + s1 */
words[i]=words[i-16]+s0+words[i-7]+s1;
}
/* 6. 進行64輪的哈希計算 SHA Compression, 64 rounds. */
/* 更新 a,b,c,d,e,f,g,h */
a=hv[0]; b=hv[1]; c=hv[2]; d=hv[3]; e=hv[4]; f=hv[5]; g=hv[6]; h=hv[7];
/* Compress for 64 rounds */
for(i=0; i<64; i++) {
/* S1 = (e rightrotate 6) xor (e rightrotate 11) xor (e rightrotate 25) */
s1=RTROT(4,e,6)^RTROT(4,e,11)^RTROT(4,e,25);
/* ch = (e and f) xor ((not e) and g) */
ch= (e&f)^((~e)&g);
/* temp1 = h + S1 + ch + kv[i] + w[i] */
temp1=h+s1+ch+kv[i]+words[i];
/* S0 = (a rightrotate 2) xor (a rightrotate 13) xor (a rightrotate 22) */
s0=RTROT(4,a,2)^RTROT(4,a,13)^RTROT(4,a,22);
/* maj = (a and b) xor (a and c) xor (b and c) */
maj=(a&b)^(a&c)^(b&c);
/* temp2 = S0 + maj */
temp2=s0+maj;
h=g;
g=f;
f=e;
e=d+temp1;
d=c;
c=b;
b=a;
a=temp1+temp2;
}
#if 1 /* 列印變數 Print a~h */
printf("a: %08x \n", a);
printf("b: %08x \n", b);
printf("c: %08x \n", c);
printf("d: %08x \n", d);
printf("e: %08x \n", e);
printf("f: %08x \n", f);
printf("g: %08x \n", g);
printf("h: %08x \n", h);
#endif
/* 7. 修改哈兮變數 Modify final values */
hv[0] += a;
hv[1] += b;
hv[2] += c;
hv[3] += d;
hv[4] += e;
hv[5] += f;
hv[6] += g;
hv[7] += h;
} /* ---- 結束所有訊息塊的計算 END: chunk loop ---- */
/* 8. 生成最終的哈希訊息摘要 Generate final hash digest */
for(i=0; i<8; i++)
sprintf((char *)digest+8*i,"%08x",hv[i]); /*Convert to string */
printf("\nDigest: %s\n", digest);
return 0;
}
在Linux系統下進行編譯和運行：
轉載請註明出處，本文鏈接：https://www.uj5u.com/qukuanlian/231481.html
標籤：區塊鏈
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