Crypto++ ECC加密

Crypto++库是一个不错的加密算法库，然而在网上，用Crypto++库来做ECC加密算法的例子很少。而且网上的例子也大都是把公钥和私钥生成到文件中，而笔者需要的是把公钥和私钥直接放到字符串中。

经过自己的搜索和试验，终于找到了实现的方法，可能不是最好的，但也算一种
解决方案。

关于Crypto++库的编译、安装方法，请自行度娘，这里就不累述了。

一、ECC加密算法

关于ECC加密算法的原理，请自行度娘，这里只列出算法的代码。

下面的代码已经在Windows 10、Visual Studio community 2015、Crypto++ 5.6.5环境下编译运行通过

** 在Visual Studio中编译时，需要将 "Properties -> C/C++ -> Code Generateion -> Runtime Library "改为 “Multi-threaded Debug (/MTd)”，如下图所示：**

头文件：ecc_encryption_algorithm.h

#ifndef ECC_ENCRYPTION_ALGORITHM_H_
#define ECC_ENCRYPTION_ALGORITHM_H_

#include<string>

class EccEncryption
{
public:
    /// This method is used to generate keys for ECC encryption algorithm
    ///
    ///  param[in]  uiKeySize, length of key
    /// param[out]  sPrivateKey, private key
    /// param[out]  sPublicKey, public key
    void GenerateEccKeys(unsigned int uiKeySize, std::string& sPrivateKey, std::string& sPublicKey);

    /// This method is used to encrypt the input message using public key
    ///
    ///  param[in]  sPublicKey, public key generated by the first method
    /// param[out]  sMsgToEncrypt, message to encryppt
    /// 
eturn  the message encrypted using the input public key
    std::string Encrypt(const std::string& sPublicKey, const std::string& sMsgToEncrypt);

    /// This method is used to decrypt the input message using private key
    ///
    /// param[in] sPrivateKey, private key used to decrypt the cipher text
    /// param[in] sMsgToDecrypt, cipher text used to decrypt to get the plain text
    /// 
eturn decrypted plain text
    std::string Decrypt(const std::string& sPrivateKey, const std::string& sMsgToDecrytp);
}; 
#endif

cpp文件： ecc_encryption_algorithm.cpp

#include "ecc_encryption_algorithm.h"
#include "eccrypto.h"
#include "osrng.h"
#include "oids.h"
#include "hex.h"
#include "filters.h"

void EccEncryption::GenerateEccKeys(unsigned int uiKeySize, std::string& sPrivateKey, std::string& sPublicKey)
{
    using namespace CryptoPP;
    // Random pool, the second parameter is the length of key
    // 随机数池，第二个参数是生成密钥的长
    AutoSeededRandomPool rnd(false, 1024);

    ECIES<ECP>::PrivateKey  privateKey;
    ECIES<ECP>::PublicKey   publicKey;
    // Generate private key
    // 生成私钥
    privateKey.Initialize(rnd, ASN1::secp521r1());
    // Generate public key using private key
    // 用私钥生成密钥
    privateKey.MakePublicKey(publicKey);

    ECIES<ECP>::Encryptor encryptor(publicKey);
    HexEncoder pubEncoder(new StringSink(sPublicKey));
    encryptor.DEREncode(pubEncoder);
    pubEncoder.MessageEnd();

    ECIES<ECP>::Decryptor decryptor(privateKey);
    HexEncoder prvEncoder(new StringSink(sPrivateKey));
    decryptor.DEREncode(prvEncoder);
    prvEncoder.MessageEnd();
}

std::string EccEncryption::Encrypt(const std::string& sPublicKey, const std::string& sMsgToEncrypt)
{
    using namespace CryptoPP;
    // If to save the keys into a file, FileSource should be replace StringSource
    // 如果需要把密钥保存到文件里，可以用 FileSource
    StringSource pubString(sPublicKey, true, new HexDecoder);
    ECIES<ECP>::Encryptor encryptor(pubString);

    // Calculate the length of cipher text
    // 计算加密后密文的长度
    size_t uiCipherTextSize = encryptor.CiphertextLength(sMsgToEncrypt.size());
    std::string sCipherText;
    sCipherText.resize(uiCipherTextSize);
    RandomPool rnd;
    encryptor.Encrypt(rnd, (byte*)(sMsgToEncrypt.c_str()), sMsgToEncrypt.size(), (byte*)(sCipherText.data()));
    return sCipherText;
}

std::string EccEncryption::Decrypt(const std::string& sPrivateKey, const std::string& sMsgToDecrytp)
{
    using namespace CryptoPP;
    StringSource privString(sPrivateKey, true, new HexDecoder);
    ECIES<ECP>::Decryptor decryptor(privString);

    auto sPlainTextLen = decryptor.MaxPlaintextLength(sMsgToDecrytp.size());
    std::string sDecryText;
    sDecryText.resize(sPlainTextLen);
    RandomPool rnd;
    decryptor.Decrypt(rnd, (byte*)sMsgToDecrytp.c_str(), sMsgToDecrytp.size(), (byte*)sDecryText.data());
    return sDecryText;
}

测试代码： test_main.h

#include "ecc_encryption_algorithm.h"
#include <iostream>

void main()
{
    std::string sStrToTest = std::string("Hello world. This is an example of Ecc
 encryption algorithm of Crypto++ open source library.");
    EccEncryption ecc;
    std::string sPrivateKey, sPublicKey;
    ecc.GenerateEccKeys(1024, sPrivateKey, sPublicKey);
      
    std::cout << "Generated private key is : "<< std::endl;
    std::cout << sPrivateKey << std::endl;
    std::cout << "***********************************************************" << std::endl;

    std::cout << "Generated public key is : "<< std::endl;
    std::cout << sPublicKey << std::endl;
    std::cout << "***********************************************************" << std::endl;

    std::cout << "The message to be encrypted is : " << std::endl;
    std::cout << sStrToTest << std::endl;
    std::cout << "***********************************************************" << std::endl;

    std::string sEncryptResult = ecc.Encrypt(sPublicKey, sStrToTest);
    std::cout << "The result of encrypt is : " << std::endl;
    std::cout << sEncryptResult << std::endl;
    std::cout << "***********************************************************" << std::endl;

    std::string sDecryptResult = ecc.Decrypt(sPrivateKey, sEncryptResult);
    std::cout << "The result of decrypt is : " << std::endl;
    std::cout << sDecryptResult << std::endl;
    std::cout << "***********************************************************" << std::endl;
}

运行结果如下图所示：