一、SHA256算法介紹與原理詳解
見博客《SHA256算法原理詳解》

二、SHA256算法C++實現
1）sha256.hpp

/* * Filename: sha256.hpp * Author: L.Y. * Brief: SHA256算法實現 * Version: V1.0.0 * Update log: * 1）20191108-20191113 V1.0.0 * 1、初次版本。 * TODO: * Attention: * 1）輸入信息中有中文時，得到的數字指紋與使用SHA256在線加密工具得到數字指紋可能不相同。 * 原因是中文的編碼方式不同。 */#ifndef SHA256_HPP #define SHA256_HPP#include <stdint.h>#include <string> #include <vector>namespace ly {// // \brief: SHA256算法實現 // class Sha256 { public://! 默認構造函數Sha256() {}//! 析構函數virtual ~Sha256() {}/** @brief: 使用SHA256算法，獲取輸入信息的摘要（數字指紋）@param[in] message: 輸入信息@param[out] _digest: 摘要（數字指紋）@return: 是否成功*/bool encrypt(const std::vector<uint8_t>& message, std::vector<uint8_t>* _digest);/** @brief: 獲取十六進制表示的信息摘要（數字指紋）@param[in] message: 輸入信息@return: 十六進制表示的信息摘要（數字指紋）*/std::string getHexMessageDigest(const std::string& message);protected:/// SHA256算法中定義的6種邏輯運算 ///inline uint32_t ch(uint32_t x, uint32_t y, uint32_t z) const;inline uint32_t maj(uint32_t x, uint32_t y, uint32_t z) const;inline uint32_t big_sigma0(uint32_t x) const;inline uint32_t big_sigma1(uint32_t x) const;inline uint32_t small_sigma0(uint32_t x) const;inline uint32_t small_sigma1(uint32_t x) const;/** @brief: SHA256算法對輸入信息的預處理，包括“附加填充比特”和“附加長度值”附加填充比特: 在報文末尾進行填充，先補第一個比特為1，然后都補0，直到長度滿足對512取模后余數是448。需要注意的是，信息必須進行填充。附加長度值: 用一個64位的數據來表示原始消息（填充前的消息）的長度，并將其補到已經進行了填充操作的消息后面。@param[in][out] _message: 待處理的信息@return: 是否成功*/bool preprocessing(std::vector<uint8_t>* _message) const;/** @brief: 將信息分解成連續的64Byte大小的數據塊@param[in] message: 輸入信息，長度為64Byte的倍數@param[out] _chunks: 輸出數據塊@return: 是否成功*/bool breakTextInto64ByteChunks(const std::vector<uint8_t>& message, std::vector<std::vector<uint8_t>>* _chunks) const;/** @brief: 由64Byte大小的數據塊，構造出64個4Byte大小的字。構造算法：前16個字直接由數據塊分解得到，其余的字由如下迭代公式得到：W[t] = small_sigma1(W[t-2]) + W[t-7] + small_sigma0(W[t-15]) + W[t-16]@param[in] chunk: 輸入數據塊，大小為64Byte@param[out] _words: 輸出字@return: 是否成功*/bool structureWords(const std::vector<uint8_t>& chunk, std::vector<uint32_t>* _words) const;/** @breif: 基于64個4Byte大小的字，進行64次循環加密@param[in] words: 64個4Byte大小的字@param[in][out] _message_digest: 信息摘要@return: 是否成功*/bool transform(const std::vector<uint32_t>& words, std::vector<uint32_t>* _message_digest) const;/** @brief: 輸出最終的哈希值（數字指紋）@param[in] input: 步長為32bit的哈希值@param[out] _output: 步長為8bit的哈希值@return: 是否成功*/bool produceFinalHashValue(const std::vector<uint32_t>& input,std::vector<uint8_t>* _output) const;private:static std::vector<uint32_t> initial_message_digest_; // 在SHA256算法中的初始信息摘要，這些常量是對自然數中前8個質數的平方根的小數部分取前32bit而來。static std::vector<uint32_t> add_constant_; // 在SHA256算法中，用到64個常量，這些常量是對自然數中前64個質數的立方根的小數部分取前32bit而來。 };// 內聯函數&模版函數的定義 /inline uint32_t Sha256::ch(uint32_t x, uint32_t y, uint32_t z) const {return (x & y) ^ ((~x) & z); }inline uint32_t Sha256::maj(uint32_t x, uint32_t y, uint32_t z) const {return (x & y) ^ (x & z) ^ (y & z); }inline uint32_t Sha256::big_sigma0(uint32_t x) const {return (x >> 2 | x << 30) ^ (x >> 13 | x << 19) ^ (x >> 22 | x << 10); }inline uint32_t Sha256::big_sigma1(uint32_t x) const {return (x >> 6 | x << 26) ^ (x >> 11 | x << 21) ^ (x >> 25 | x << 7); }inline uint32_t Sha256::small_sigma0(uint32_t x) const {return (x >> 7 | x << 25) ^ (x >> 18 | x << 14) ^ (x >> 3); }inline uint32_t Sha256::small_sigma1(uint32_t x) const {return (x >> 17 | x << 15) ^ (x >> 19 | x << 13) ^ (x >> 10); }} // namespace ly#endif // SHA256_HPP

2）sha256.cpp

/* * Filename: sha256.cpp * Author: L.Y. * Brief: SHA256算法實現 * Version: V1.0.0 * Update log: * 1）20191108-20191113 V1.0.0 * 1、初次版本。 * TODO: * Attention: * 1）輸入信息中有中文時，得到的數字指紋與使用SHA256在線加密工具得到數字指紋可能不相同。 * 原因是中文的編碼方式不同。 */#include "sha256.hpp"#include <iomanip> #include <sstream> #include <string> #include <vector>namespace ly {std::vector<uint32_t> Sha256::initial_message_digest_ = { 0x6a09e667, 0xbb67ae85, 0x3c6ef372,0xa54ff53a, 0x510e527f, 0x9b05688c,0x1f83d9ab, 0x5be0cd19 };std::vector<uint32_t> Sha256::add_constant_ = {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 };bool Sha256::encrypt(const std::vector<uint8_t>& input_message, std::vector<uint8_t>* _digest) {if (!input_message.empty() && _digest){//! 文本預處理std::vector<uint8_t> message = input_message;preprocessing(&message);//! 將文本分解成連續的64Byte大小的數據塊std::vector<std::vector<uint8_t>> chunks;breakTextInto64ByteChunks(message, &chunks);//! 由64Byte大小的數據塊，構造出64個4Byte大小的字。然后進行循環迭代。std::vector<uint32_t> message_digest(initial_message_digest_); // 初始化信息摘要std::vector<uint32_t> words;for (const auto& chunk : chunks){structureWords(chunk, &words);transform(words, &message_digest);}//! 獲取最終結果produceFinalHashValue(message_digest, _digest);return true;}else{return false;} }std::string Sha256::getHexMessageDigest(const std::string& message) {if (!message.empty()){std::vector<uint8_t> __message;for (auto it = message.begin(); it != message.end(); ++it){__message.push_back(static_cast<uint8_t>(*it));}std::vector<uint8_t> digest;encrypt(__message, &digest);std::ostringstream o_s;o_s << std::hex << std::setiosflags(std::ios::uppercase);for (auto it = digest.begin(); it != digest.end(); ++it){o_s << std::setw(2) << std::setfill('0')<< static_cast<unsigned short>(*it);}return o_s.str();}else{return "";} }bool Sha256::preprocessing(std::vector<uint8_t>* _message) const {if (_message){const uint64_t original_bit_size = _message->size() * 8;//! 附加填充比特size_t remainder = _message->size() % 64;if (remainder < 56){_message->push_back(0x80); // ox80 == 10000000for (size_t i = 1; i < 56 - remainder; ++i){_message->push_back(0x00);}}else if (remainder == 56){_message->push_back(0x80);for (size_t i = 1; i < 64; ++i){_message->push_back(0x00);}}else{_message->push_back(0x80);for (size_t i = 1; i < 64 - remainder + 56; ++i){_message->push_back(0x00);}}//! 附加原始文本的長度值for (int i = 1; i <= 8; ++i){uint8_t c = static_cast<uint8_t>(original_bit_size >> (64 - 8 * i));_message->push_back(c);}return true;}else{return false;} }bool Sha256::breakTextInto64ByteChunks(const std::vector<uint8_t>& message, std::vector<std::vector<uint8_t>>* _chunks) const {if (_chunks && 0 == message.size() % 64){_chunks->clear(); // 清空輸出buffersize_t quotient = message.size() / 64;for (size_t i = 0; i < quotient; ++i){std::vector<uint8_t> temp(message.begin() + i * 64, message.begin() + (i + 1) * 64);_chunks->push_back(temp);}return true;}else{return false;} }bool Sha256::structureWords(const std::vector<uint8_t>& chunk, std::vector<uint32_t>* _words) const {if (_words && 64 == chunk.size()){_words->resize(64);auto& words = *_words;for (int i = 0; i < 16; ++i){words[i] = (static_cast<uint32_t>(chunk[i * 4]) << 24)| (static_cast<uint32_t>(chunk[i * 4 + 1]) << 16)| (static_cast<uint32_t>(chunk[i * 4 + 2]) << 8)| static_cast<uint32_t>(chunk[i * 4 + 3]);}for (int i = 16; i < 64; ++i){words[i] = small_sigma1(words[i - 2])+ words[i - 7]+ small_sigma0(words[i - 15])+ words[i - 16];}return true;}else{return false;} }bool Sha256::transform(const std::vector<uint32_t>& words, std::vector<uint32_t>* _message_digest) const {if (_message_digest && 8 == _message_digest->size() && 64 == words.size()){std::vector<uint32_t> d = *_message_digest;for (int i = 0; i < 64; ++i){uint32_t temp1 = d[7] + big_sigma1(d[4]) + ch(d[4], d[5], d[6]) + add_constant_[i] + words[i];uint32_t temp2 = big_sigma0(d[0]) + maj(d[0], d[1], d[2]);d[7] = d[6];d[6] = d[5];d[5] = d[4];d[4] = d[3] + temp1;d[3] = d[2];d[2] = d[1];d[1] = d[0];d[0] = temp1 + temp2;}for (int i = 0; i < 8; ++i){(*_message_digest)[i] += d[i];}return true;}else{return false;} }bool Sha256::produceFinalHashValue(const std::vector<uint32_t>& input, std::vector<uint8_t>* _output) const {if (_output){_output->clear();for (auto it = input.begin(); it != input.end(); ++it){for (int i = 0; i < 4; i++){_output->push_back(static_cast<uint8_t>((*it) >> (24 - 8 * i)));}}return true;}else{return false;} }} // namespace ly

3）main.cpp

/* * Filename: main.cpp * Author: L.Y. * Brief: SHA256算法測試 */#include <iostream> #include <string>#include "sha256.hpp"int main() {std::string message = "seek truth from facts"; // 待加密的信息ly::Sha256 sha256; // 初始化Sha256對象std::string message_digest = sha256.getHexMessageDigest(message); // 加密std::cout << message_digest << std::endl; // 輸出加密結果getchar();return 0; }

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