基于Crypto++/Cryptopp的rsa密钥生成，rsa加密、解密，rsa签名、验签

转载于http://www.xdty.org/1678

在项目中需要增加一个注册的功能，想到了用rsa非对称加密的方法。对比了openssl等第三方库，最后采用了Cryptopp。

1.源文件整理
可以在http://www.cryptopp.com/获取库的源文件，解压后将文件重新归档。头文件放置到include文件夹，cpp放到src目录。同时去除所有的test相关的cpp及非cpp、h文件。拷本cryptopp目录到工程目录下
2.加入工程
在vs2010工程中增加新的filter，命名为Cryptopp，再增加子filter include和src。将include下的h文件导入到include，将src下的cpp导入到src filter。

3.编译
打开src，选中所有的cpp文件，更改属性，将预编译头改为pch.h。将工程的vc++路径更新，增加include和src。


编译工程，如果编译不过修改一下错误。
4.生成rsa公钥、私钥，经过base64编码后保存到文件
需要导入一些头文件：

#include "iterhash.h"
#include "files.h"
#include "rsa.h"
#include "randpool.h"
#include "hex.h"
#include "base64.h"
#include "osrng.h"

void CKeyController::GenerateRSAKey(unsigned int keyLength, CString decFilename, CString encFilename, CString seed)
{
    RandomPool randPool;
    randPool.Put((byte *)seed.GetBuffer(seed.GetLength()), seed.GetLength());

    RSAES_OAEP_SHA_Decryptor decrypt(randPool, keyLength);
    HexEncoder decFile(new Base64Encoder(new FileSink(decFilename.GetBuffer(decFilename.GetLength()))));

    decrypt.DEREncode(decFile);
    decFile.MessageEnd();

    RSAES_OAEP_SHA_Encryptor encrypt(decrypt);
    HexEncoder encFile(new Base64Encoder(new FileSink(encFilename.GetBuffer(encFilename.GetLength()))));
    encrypt.DEREncode(encFile);

    encFile.MessageEnd();

    return;
}
RandomPool & CKeyController::GlobalRNG()
{
    static RandomPool randomPool;
    return randomPool;
}

5.通过生成的公钥文件加密字符串

CString CKeyController::RSAEncryptString( CString encFilename, CString seed, CString message )
{
    string encString;
    FileSource encFile( encFilename.GetBuffer(encFilename.GetLength()), true, new Base64Decoder(new StringSink(encString)) );
    HexDecoder decoder;
    decoder.Put( (byte*)encString.c_str(), encString.size() );
    decoder.MessageEnd();

    RSAES_OAEP_SHA_Encryptor enc;
    enc.AccessKey().Load(decoder);

    RandomPool randPool;
    randPool.Put( (byte *)seed.GetBuffer(seed.GetLength()), seed.GetLength() );

    string result;
    StringSource( c2s(message), true, new PK_EncryptorFilter(randPool, enc, new HexEncoder(new StringSink(result))) );

    return CString(result.c_str());
}

6.通过生成的私钥文件解密字符串、

CString CKeyController::RSADecryptString( CString decFilename, CString ciphertext )
{
    string decString;
    FileSource decFile( decFilename.GetBuffer(decFilename.GetLength()), true, new Base64Decoder(new StringSink(decString)) );
    HexDecoder decoder;
    decoder.Put( (byte*)decString.c_str(), decString.size() );
    decoder.MessageEnd();

    RSAES_OAEP_SHA_Decryptor dec;
    dec.AccessKey().Load(decoder);

    string result;
    StringSource( c2s(ciphertext), true, new HexDecoder(new PK_DecryptorFilter(GlobalRNG(), dec, new StringSink(result))) );

    return CString(result.c_str());
}

7.使用私钥签名

CString CKeyController::SignMessage( const std::string& privateKeyFileName, const std::string& message )
{
    std::string signedMessage = "";
    string encString;
    FileSource privFile( privateKeyFileName.c_str(), true, new Base64Decoder(new StringSink(encString)));
    RSASSA_PKCS1v15_SHA_Signer priv;

    HexDecoder decoder;
    decoder.Put( (byte*)encString.c_str(), encString.size() );
    decoder.MessageEnd();

    priv.AccessKey().Load(decoder);

    AutoSeededRandomPool rng;
    StringSource s1(message, true, new SignerFilter(rng, priv, new HexEncoder(new StringSink(signedMessage))));

    return CString(signedMessage.c_str());
}

8.使用公钥验证签名

bool CKeyController::VerifySignature( const std::string& publicKeyFileName, const std::string& message, const std::string& signedMessage )
{
    string decString;
    FileSource pubFile( publicKeyFileName.c_str(), true, new Base64Decoder(new StringSink(decString)) );
    RSASSA_PKCS1v15_SHA_Verifier pub;

    HexDecoder decoder;
    decoder.Put( (byte*)decString.c_str(), decString.size() );
    decoder.MessageEnd();

    pub.AccessKey().Load(decoder);

    StringSource signatureFile( signedMessage, true, new HexDecoder);
    if (signatureFile.MaxRetrievable() != pub.SignatureLength())
    { throw std::string( "Signature Size Problem" ); }

    SecByteBlock signature(pub.SignatureLength());
    signatureFile.Get(signature, signature.size());

    VerifierFilter *verifierFilter = new VerifierFilter(pub);
    verifierFilter->Put(signature, pub.SignatureLength());
    StringSource s(message, true, verifierFilter);

    return verifierFilter->GetLastResult();
}

9.测试函数调用

void CKeyController::testRSA()
{
    CString encryptKey = _T("key.pub");
    CString decryptKey = _T("key.pri");
    CString seed = _T("seed");

    //GenerateRSAKey( 1024, decryptKey, encryptKey, seed );

    CString message = _T("X3BA-9NSF-8N9Q-UWQC-U7FX-AZZF-JAJW");

    CString encryptedText = RSAEncryptString( encryptKey, seed, message );

    CString decryptedText = RSADecryptString( decryptKey, encryptedText );

    CString signedMessage = SignMessage("key.pri", c2s(decryptedText));

    bool verified = VerifySignature("key.pub", c2s(message), c2s(signedMessage));
}

10.工具函数如base64转码，字符串转换

std::string CKeyController::EncodeBase64( string message )
{
    string encode;
    StringSource(message, true, new Base64Encoder(new StringSink(encode)));
    return encode;
}

std::string CKeyController::DecodeBase64( string message )
{
    string decode;
    StringSource(message, true, new Base64Decoder(new StringSink(decode)));
    return decode;
}

CString CKeyController::hashString( CString message )
{
    string digest;
    SHA256 hash;
    StringSource foo(c2s(message), true, new HashFilter(hash, new HexEncoder(new StringSink(digest))));
    return CString(digest.c_str());
}

CString CKeyController::hashFile( CString fileName )
{
    string digest;
    SHA256 hash;
    FileSource(fileName, true, new HashFilter(hash, new HexEncoder(new StringSink(digest))));
    return CString(digest.c_str());
}

std::string c2s( CString &cs )
{
    CT2CA pszConvertedAnsiString(cs);
    std::string strStd(pszConvertedAnsiString);
    return strStd;
}