《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());