《ASCE1885的信息安全》のCrypto++用户手册のrsa.h

Crypto++用户手册のrsa.h：
与RSA加解密相关的类都是在rsa.h头文件中定义的。其中类RSAFunction和类InvertibleRSAFunction是分别封装了RSA公钥和私钥信息的基础类，这两个类支持直接通过函数ApplyFunction （公钥操作）和函数CalculateInverse（私钥操作）进行RSA的计算。我们只有在完全清楚自己的操作的情况下，同时使用正确
补位（padding），才能直接使用这两个函数。
一般情况下，我们更多使用的是rsa.h中通过typedef定义的类型：
typedef RSAES<OAEP<SHA> >::Decryptor RSAES_OAEP_SHA_Decryptor;
typedef RSAES<OAEP<SHA> >::Encryptor RSAES_OAEP_SHA_Encryptor;
 
typedef RSASS<PKCS1v15, SHA>::Signer RSASSA_PKCS1v15_SHA_Signer;
typedef RSASS<PKCS1v15, SHA>::Verifier RSASSA_PKCS1v15_SHA_Verifier;
….
由这些类型定义的类是从pubkey.h文件中的基类派生而来的，各种的RSA Encryptor/Decryptor/Signer/Verifier类型定义使用起来会很简单，只要我们记住它们最终是从定义在cryptlib.h文件中的PK_FixedLengthEncryptor, PK_FixedLengthDecryptor, PK_Signer 或 PK_Verifier继承而来就行了。
 
下面来看几个实例吧：

1）生成RSA密钥对并保存之：
// InvertibleRSAFunction is used directly only because the private key
 // won't actually be used to perform any cryptographic operation;
 // otherwise, an appropriate typedef'ed type from rsa.h would have been used.
 AutoSeededRandomPool rng;
 InvertibleRSAFunction privkey(rng, 1024);
 
 // With the current version of Crypto++, MessageEnd() needs to be called
 // explicitly because Base64Encoder doesn't flush its buffer on destruction.
 Base64Encoder privkeysink(new FileSink("c://privkey.txt"));
 privkey.DEREncode(privkeysink);
 privkeysink.MessageEnd();
 
 // Suppose we want to store the public key separately,
 // possibly because we will be sending the public key to a third party.
 RSAFunction pubkey(privkey);
 
 Base64Encoder pubkeysink(new FileSink("c://pubkey.txt"));
 pubkey.DEREncode(pubkeysink);
 pubkeysink.MessageEnd();
 
2）加载私钥，并用它对文件进行签名：
string strContents;
 FileSource("c://tobesigned.dat", true,
     new StringSink(strContents));
 
 RSASSA_PKCS1v15_SHA_Signer privkey(
     FileSource("c://privkey.txt", true,
         new Base64Decoder)));
 
 SecByteBlock sbbSignature(privkey.SignatureLength());
 
 AutoSeededRandomPool rng;
 privkey.SignMessage(
     rng,
     (byte const*) strContents.data(),
     strContents.size(),
     sbbSignature.Begin());
 
 FileSink sink("c://signed.dat");
 sink.Put((byte const*) strContents.data(), strContents.size());
 sink.Put(sbbSignature.Begin(), sbbSignature.Size());
 
3）加载公钥，并用它对一短字符串进行RSA加密：
string strShortString =
     "Must be shorter than the size of the RSA key minus OAEP decoration.";
 
 RSAES_OAEP_SHA_Encryptor pubkey(
     FileSource("c://pubkey.txt", true,
         new Base64Decoder)));
 
 // Cannot use std::string for buffer;
 // its internal storage might not be contiguous
 SecByteBlock sbbCipherText(pubkey.CipherTextLength(strShortString.size()));
 
 AutoSeededRandomPool rng;
 pubkey.Encrypt(
     rng,
     (byte const*) strShortString.data(),
     strShortString.size(),
     sbbCipherText.Begin());
 
 FileSink("c://encrypted.dat").Put(sbbCipherText.Begin(), sbbCipherText.Size());