《ASCE1885的信息安全》のCrypto++用户手册のeccrypto.h

eccrypto.h提供了基于椭圆曲线加密操作的一系列模板类，将这些类设计成模板主要的原因是有两种类型椭圆曲线。因此，类EC2N(ec2n.h)代表的是基于GF(2ⁿ)的椭圆曲线算法；而类ECP(ecp.h)代表的是基于GF(p)的椭圆曲线算法。

椭圆曲线的参数保存在模板类ECParameters中，参数能够以多种方式初始化；但是其中一个更实用的用法是使用函数LoadRecommendedParameters()，它提供了建议参数之一，定义在oids.h中。

下面看几个实例代码：

1）生成一个EC2N密钥对，并保存之：

// ECPrivateKey is used directly only because the private key

 // won't actually be used to perform any cryptographic operation.

 AutoSeededRandomPool rng;

 ECPrivateKey privkey(rng, ASN1::sect233k1);

 

 Base64Encoder privkeysink(new FileSink("c://privkey.txt"));

 privkey.DEREncode(privkeysink);

 privkeysink.MessageEnd();   // Need to flush Base64Encoder's buffer

 

 // Suppose we want to store the public key separately,

 // possibly because we will be sending the public key to a third party.

 ECPublicKey pubkey(privkey);

 

 Base64Encoder pubkeysink(new FileSink("c://pubkey.txt"));

 pubkey.DEREncode(pubkeysink);

 pubkeysink.MessageEnd();    // Need to flush Base64Encoder's buffer

 

2）加载公钥，并加密一个文件：

string sContents;

 FileSource("c://tobesigned.dat", true,

     new StringSink(sContents));

 

 ECEncryptor 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(sContents.size()));

 

 // ECIES encryption is nice because it handles the entire encryption

 // process internally, regardless of the length of input data.

 // We don't have to generate a symmetric session key and encrypt

 // with it separately.

 AutoSeededRandomPool rng;

 pubkey.Encrypt(

     rng,

     (byte const*) sContents.data(),

     sContents.size(),

     sbbCipherText.Begin());

 

 FileSink("c://encrypted.dat").Put(sbbCipherText.Begin(), sbbCipherText.Size());