《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());