本文主要參考《基於FPGA的SHA256高效數字加密系統_劉鈺力_第三章》（如果有條件請直接下載原論文）以及bitcoin源碼
需要注意的是，本系列不注重對比特幣框架解析（我現在也沒這個能力），而是主要着眼於相關基礎數據結構和算法的實現。
前排提醒，本人新手，如有問題，還望指正。
福來妹鎮樓
SHA256算法是美國聯邦信息處理標准提出的一個標准算法。其有六個邏輯函數，兩個移位函數以及8個初始化哈希值。所有函數的操作均是以32bit的數據塊為單位進行運算的，同時所有的加法操作都是模232的加法。
函數具體內容如下：
移位函數：
SHRn(x) = x >> n;
ROTRn(x) = (x << n) (x >> w - n)
SHA256根據算法的要求一共可以分為4個部分，分別為：附件填充數據信息、數據塊擴展模塊、循環迭代計算模塊和哈希值輸出模塊。下面是對這四個模塊的詳細描述。
1、附加填充數據信息
2、數據塊拓展
3、循環迭代運算
在循環迭代預計算這個部分里主要完成的工作是，計算出當前512bits的哈希值，具體內容如下：
4）重復1-3直到所有的數據被處理完畢。
如果你的動手能力比較強，那么我想看完上面的算法應該可以手擼出來了。
那么在bitcoin中是怎么實現上述算法的呢？
#include <string.h> #include<iostream> typedef unsigned int uint32_t; namespace sha256 { // SHA256函數所使用的6個邏輯函數 uint32_t inline Ch(uint32_t x, uint32_t y, uint32_t z) { return z ^ (x & (y ^ z)); } uint32_t inline Maj(uint32_t x, uint32_t y, uint32_t z) { return (x & y) | (z & (x | y)); } uint32_t inline Sigma0(uint32_t x) { return (x >> 2 | x << 30) ^ (x >> 13 | x << 19) ^ (x >> 22 | x << 10); } uint32_t inline Sigma1(uint32_t x) { return (x >> 6 | x << 26) ^ (x >> 11 | x << 21) ^ (x >> 25 | x << 7); } uint32_t inline sigma0(uint32_t x) { return (x >> 7 | x << 25) ^ (x >> 18 | x << 14) ^ (x >> 3); } uint32_t inline sigma1(uint32_t x) { return (x >> 17 | x << 15) ^ (x >> 19 | x << 13) ^ (x >> 10); } /** SHA-256需要做64次循環計算中的單次計算函數 */ //one round of SHA256 void inline Round(uint32_t a, uint32_t b, uint32_t c, uint32_t& d, uint32_t e, uint32_t f, uint32_t g, uint32_t& h, uint32_t k, uint32_t w) { uint32_t t1 = h + Sigma1(e) + Ch(e, f, g) + k + w; uint32_t t2 = Sigma0(a) + Maj(a, b, c); d += t1; h = t1 + t2; } // 將變量轉換為小端(little endia) //這主要是由於電腦（x86）是小端的， //不過源碼部分這里是大端，應該是和網絡相關吧 uint32_t static inline ReadLE32(const unsigned char* ptr) { uint32_t x; memcpy((char*)&x, ptr, 4); return (((x & 0xff000000U) >> 24) | ((x & 0x00ff0000U) >> 8) | ((x & 0x0000ff00U) << 8) | ((x & 0x000000ffU) << 24)); } //64次循環計算 void Transform(uint32_t* s, const unsigned char* chunk, size_t blocks) { while (blocks--) { uint32_t a = s[0], b = s[1], c = s[2], d = s[3], e = s[4], f = s[5], g = s[6], h = s[7]; uint32_t w0, w1, w2, w3, w4, w5, w6, w7, w8, w9, w10, w11, w12, w13, w14, w15; Round(a, b, c, d, e, f, g, h, 0x428a2f98, w0 = ReadLE32(chunk + 0)); Round(h, a, b, c, d, e, f, g, 0x71374491, w1 = ReadLE32(chunk + 4)); Round(g, h, a, b, c, d, e, f, 0xb5c0fbcf, w2 = ReadLE32(chunk + 8)); Round(f, g, h, a, b, c, d, e, 0xe9b5dba5, w3 = ReadLE32(chunk + 12)); Round(e, f, g, h, a, b, c, d, 0x3956c25b, w4 = ReadLE32(chunk + 16)); Round(d, e, f, g, h, a, b, c, 0x59f111f1, w5 = ReadLE32(chunk + 20)); Round(c, d, e, f, g, h, a, b, 0x923f82a4, w6 = ReadLE32(chunk + 24)); Round(b, c, d, e, f, g, h, a, 0xab1c5ed5, w7 = ReadLE32(chunk + 28)); Round(a, b, c, d, e, f, g, h, 0xd807aa98, w8 = ReadLE32(chunk + 32)); Round(h, a, b, c, d, e, f, g, 0x12835b01, w9 = ReadLE32(chunk + 36)); Round(g, h, a, b, c, d, e, f, 0x243185be, w10 = ReadLE32(chunk + 40)); Round(f, g, h, a, b, c, d, e, 0x550c7dc3, w11 = ReadLE32(chunk + 44)); Round(e, f, g, h, a, b, c, d, 0x72be5d74, w12 = ReadLE32(chunk + 48)); Round(d, e, f, g, h, a, b, c, 0x80deb1fe, w13 = ReadLE32(chunk + 52)); Round(c, d, e, f, g, h, a, b, 0x9bdc06a7, w14 = ReadLE32(chunk + 56)); Round(b, c, d, e, f, g, h, a, 0xc19bf174, w15 = ReadLE32(chunk + 60)); Round(a, b, c, d, e, f, g, h, 0xe49b69c1, w0 += sigma1(w14) + w9 + sigma0(w1)); Round(h, a, b, c, d, e, f, g, 0xefbe4786, w1 += sigma1(w15) + w10 + sigma0(w2)); Round(g, h, a, b, c, d, e, f, 0x0fc19dc6, w2 += sigma1(w0) + w11 + sigma0(w3)); Round(f, g, h, a, b, c, d, e, 0x240ca1cc, w3 += sigma1(w1) + w12 + sigma0(w4)); Round(e, f, g, h, a, b, c, d, 0x2de92c6f, w4 += sigma1(w2) + w13 + sigma0(w5)); Round(d, e, f, g, h, a, b, c, 0x4a7484aa, w5 += sigma1(w3) + w14 + sigma0(w6)); Round(c, d, e, f, g, h, a, b, 0x5cb0a9dc, w6 += sigma1(w4) + w15 + sigma0(w7)); Round(b, c, d, e, f, g, h, a, 0x76f988da, w7 += sigma1(w5) + w0 + sigma0(w8)); Round(a, b, c, d, e, f, g, h, 0x983e5152, w8 += sigma1(w6) + w1 + sigma0(w9)); Round(h, a, b, c, d, e, f, g, 0xa831c66d, w9 += sigma1(w7) + w2 + sigma0(w10)); Round(g, h, a, b, c, d, e, f, 0xb00327c8, w10 += sigma1(w8) + w3 + sigma0(w11)); Round(f, g, h, a, b, c, d, e, 0xbf597fc7, w11 += sigma1(w9) + w4 + sigma0(w12)); Round(e, f, g, h, a, b, c, d, 0xc6e00bf3, w12 += sigma1(w10) + w5 + sigma0(w13)); Round(d, e, f, g, h, a, b, c, 0xd5a79147, w13 += sigma1(w11) + w6 + sigma0(w14)); Round(c, d, e, f, g, h, a, b, 0x06ca6351, w14 += sigma1(w12) + w7 + sigma0(w15)); Round(b, c, d, e, f, g, h, a, 0x14292967, w15 += sigma1(w13) + w8 + sigma0(w0)); Round(a, b, c, d, e, f, g, h, 0x27b70a85, w0 += sigma1(w14) + w9 + sigma0(w1)); Round(h, a, b, c, d, e, f, g, 0x2e1b2138, w1 += sigma1(w15) + w10 + sigma0(w2)); Round(g, h, a, b, c, d, e, f, 0x4d2c6dfc, w2 += sigma1(w0) + w11 + sigma0(w3)); Round(f, g, h, a, b, c, d, e, 0x53380d13, w3 += sigma1(w1) + w12 + sigma0(w4)); Round(e, f, g, h, a, b, c, d, 0x650a7354, w4 += sigma1(w2) + w13 + sigma0(w5)); Round(d, e, f, g, h, a, b, c, 0x766a0abb, w5 += sigma1(w3) + w14 + sigma0(w6)); Round(c, d, e, f, g, h, a, b, 0x81c2c92e, w6 += sigma1(w4) + w15 + sigma0(w7)); Round(b, c, d, e, f, g, h, a, 0x92722c85, w7 += sigma1(w5) + w0 + sigma0(w8)); Round(a, b, c, d, e, f, g, h, 0xa2bfe8a1, w8 += sigma1(w6) + w1 + sigma0(w9)); Round(h, a, b, c, d, e, f, g, 0xa81a664b, w9 += sigma1(w7) + w2 + sigma0(w10)); Round(g, h, a, b, c, d, e, f, 0xc24b8b70, w10 += sigma1(w8) + w3 + sigma0(w11)); Round(f, g, h, a, b, c, d, e, 0xc76c51a3, w11 += sigma1(w9) + w4 + sigma0(w12)); Round(e, f, g, h, a, b, c, d, 0xd192e819, w12 += sigma1(w10) + w5 + sigma0(w13)); Round(d, e, f, g, h, a, b, c, 0xd6990624, w13 += sigma1(w11) + w6 + sigma0(w14)); Round(c, d, e, f, g, h, a, b, 0xf40e3585, w14 += sigma1(w12) + w7 + sigma0(w15)); Round(b, c, d, e, f, g, h, a, 0x106aa070, w15 += sigma1(w13) + w8 + sigma0(w0)); Round(a, b, c, d, e, f, g, h, 0x19a4c116, w0 += sigma1(w14) + w9 + sigma0(w1)); Round(h, a, b, c, d, e, f, g, 0x1e376c08, w1 += sigma1(w15) + w10 + sigma0(w2)); Round(g, h, a, b, c, d, e, f, 0x2748774c, w2 += sigma1(w0) + w11 + sigma0(w3)); Round(f, g, h, a, b, c, d, e, 0x34b0bcb5, w3 += sigma1(w1) + w12 + sigma0(w4)); Round(e, f, g, h, a, b, c, d, 0x391c0cb3, w4 += sigma1(w2) + w13 + sigma0(w5)); Round(d, e, f, g, h, a, b, c, 0x4ed8aa4a, w5 += sigma1(w3) + w14 + sigma0(w6)); Round(c, d, e, f, g, h, a, b, 0x5b9cca4f, w6 += sigma1(w4) + w15 + sigma0(w7)); Round(b, c, d, e, f, g, h, a, 0x682e6ff3, w7 += sigma1(w5) + w0 + sigma0(w8)); Round(a, b, c, d, e, f, g, h, 0x748f82ee, w8 += sigma1(w6) + w1 + sigma0(w9)); Round(h, a, b, c, d, e, f, g, 0x78a5636f, w9 += sigma1(w7) + w2 + sigma0(w10)); Round(g, h, a, b, c, d, e, f, 0x84c87814, w10 += sigma1(w8) + w3 + sigma0(w11)); Round(f, g, h, a, b, c, d, e, 0x8cc70208, w11 += sigma1(w9) + w4 + sigma0(w12)); Round(e, f, g, h, a, b, c, d, 0x90befffa, w12 += sigma1(w10) + w5 + sigma0(w13)); Round(d, e, f, g, h, a, b, c, 0xa4506ceb, w13 += sigma1(w11) + w6 + sigma0(w14)); Round(c, d, e, f, g, h, a, b, 0xbef9a3f7, w14 + sigma1(w12) + w7 + sigma0(w15)); Round(b, c, d, e, f, g, h, a, 0xc67178f2, w15 + sigma1(w13) + w8 + sigma0(w0)); s[0] += a; s[1] += b; s[2] += c; s[3] += d; s[4] += e; s[5] += f; s[6] += g; s[7] += h; chunk += 64; } } } // namespace sha256 //函數指針 typedef void (*TransformType)(uint32_t*, const unsigned char*, size_t); TransformType tr = sha256::Transform; //測試函數，使用的是bitcoin源碼中的自測函數 //注意，這里並沒有第一步填充信息，是因為信息已經填充好了 //填充信息部分並不難，如果不出意外會在下一篇merkle tree的文章中會給出 int main() { // static const unsigned char in1[65] = {0, 0x80}; static const unsigned char in2[129] = { 0, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 32, 0x80, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0 }; /**SHA256函數所使用的8個32bit初始化哈希值 */ static const uint32_t init[8] = {0x6a09e667ul, 0xbb67ae85ul, 0x3c6ef372ul, 0xa54ff53aul, 0x510e527ful, 0x9b05688cul, 0x1f83d9abul, 0x5be0cd19ul}; //測試結果 static const uint32_t out1[8] = {0xe3b0c442ul, 0x98fc1c14ul, 0x9afbf4c8ul, 0x996fb924ul, 0x27ae41e4ul, 0x649b934cul, 0xa495991bul, 0x7852b855ul}; static const uint32_t out2[8] = {0xce4153b0ul, 0x147c2a86ul, 0x3ed4298eul, 0xe0676bc8ul, 0x79fc77a1ul, 0x2abe1f49ul, 0xb2b055dful, 0x1069523eul}; uint32_t buf[8]; memcpy(buf, init, sizeof(buf)); // Process nothing, and check we remain in the initial state. tr(buf, NULL, 0); if (memcmp(buf, init, sizeof(buf))) std::cout << "False\n"; else std::cout << "True\n"; // Process the padded empty string (unaligned) tr(buf, in1 + 1, 1); if (memcmp(buf, out1, sizeof(buf))) std::cout << "False\n"; else std::cout << "True\n"; // Process 64 spaces (unaligned) memcpy(buf, init, sizeof(buf)); tr(buf, in2 + 1, 2); if (memcmp(buf, out2, sizeof(buf))) std::cout << "False" << std::endl; else std::cout << "True" << std::endl; return 0; }
差不多就是這樣了。
下一篇，merkle tree相關