《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());