代码片段：Crypto++使用方法汇总

今天来说简单汇总一下著名C++编解码库Crypto++的使用方法，以下仅列出代码片段，详细的API解释请大家参考在Crypto++官网文档。
基本上这个库的调用方式比较少见，但是学会了其中一种，其他的算法函数也是可以融会贯通的。

1) AES加密：

string m_buf;
CryptoPP::AES::Encryption aes_encryption(m_key, CryptoPP::AES::MAX_KEYLENGTH);
CryptoPP::CBC_Mode_ExternalCipher::Encryption cbc_encryption(aes_encryption, m_iv);
CryptoPP::StreamTransformationFilter cbc_encryptor(cbc_encryption, new CryptoPP::HexEncoder(new CryptoPP::StringSink(m_buf)));
cbc_encryptor.Put(reinterpret_cast<const byte *>(plain_str.c_str()), plain_str.length());
cbc_encryptor.MessageEnd();

2) AES解密：

string m_buf;
CryptoPP::CBC_Mode<CryptoPP::AES>::Decryption cbc_decryption(m_key, CryptoPP::AES::MAX_KEYLENGTH, m_iv);
CryptoPP::HexDecoder decryptor(new CryptoPP::StreamTransformationFilter(cbc_decryption, new CryptoPP::StringSink(m_buf)));
decryptor.Put(reinterpret_cast<const byte *>(cipher_A.GetBuffer()), cipher_A.GetLength());
decryptor.MessageEnd();

3) Base64编码：

string cipher;
CryptoPP::StringSource(plain, length_in, true, new CryptoPP::Base64Encoder(new CryptoPP::StringSink(cipher), false));

4) Base64解码：

string cipher_str;
CryptoPP::StringSource(cipher_str, true, new CryptoPP::Base64Decoder(new CryptoPP::StringSink(m_buf)));

5) 对文件进行MD5:

CryptoPP::Weak1::MD5 md5;
CryptoPP::FileSource(path, true, new CryptoPP::HashFilter(md5, new CryptoPP::HexEncoder(new CryptoPP::StringSink(str))));

6) Hex编码：

string encoded("");
CryptoPP::StringSource ss(bin, length, true, new CryptoPP::HexEncoder(new CryptoPP::StringSink(encoded)));

7) Hex解密：

string bin("");
CryptoPP::StringSource ssk(hexA, true, new CryptoPP::HexDecoder(new CryptoPP::StringSink(bin)));

8）RSA加密：

void CRSACore::EncryptString(const string &strPub, const char *Seed, const string &Plaintext, string &Ciphertext)
{
	CryptoPP::StringSource PublicKey(strPub, true, new CryptoPP::HexDecoder);
	CryptoPP::RSAES_OAEP_SHA_Encryptor Pub(PublicKey);

	CryptoPP::RandomPool RandPool;
	RandPool.IncorporateEntropy((byte *)Seed, strlen(Seed));

	int MaxMsgLength = (int)Pub.FixedMaxPlaintextLength();
	for (int i = (int)Plaintext.size(), j=0; i > 0; i -= MaxMsgLength, j += MaxMsgLength)
	{
		string PartPlaintext = Plaintext.substr(j, MaxMsgLength);
		string PartCiphertext;
		CryptoPP::StringSource(PartPlaintext, true, new CryptoPP::PK_EncryptorFilter(RandPool, Pub, new CryptoPP::HexEncoder(new CryptoPP::StringSink(PartCiphertext))));
		Ciphertext += PartCiphertext;                  
	}
}

9) RSA解密：

CryptoPP::StringSource PrivKey(strPriv, true, new CryptoPP::HexDecoder);
CryptoPP::RSAES_OAEP_SHA_Decryptor Priv(PrivKey);
CryptoPP::RandomPool rand_poll;

// indicate the ciphertext in hexcode
int CiphertextLength = (int)Priv.FixedCiphertextLength() * 2;
for (int i = (int)Ciphertext.size(), j=0; i > 0; i -= CiphertextLength, j += CiphertextLength)
{
	string PartCiphertext = Ciphertext.substr(j, CiphertextLength);
	string PartPlaintext;
	CryptoPP::StringSource(PartCiphertext, true, new CryptoPP::HexDecoder(new CryptoPP::PK_DecryptorFilter(rand_poll, Priv, new CryptoPP::StringSink(PartPlaintext))));
	Plaintext += PartPlaintext;
}