DSA-Digital Signature Algorithm(Schnorr和ElGamal签名算法的变种)

package com.ice.webos.util.security;

import java.security.Key;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.DSAPublicKey;
import java.security.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;

/**
* DSA-Digital Signature Algorithm
* 是Schnorr和ElGamal签名算法的变种，被美国NIST作为DSS(DigitalSignature Standard)。<br>
* 简单的说，这是一种更高级的验证方式，用作数字签名。<br>
* 不单单只有公钥、私钥，还有数字签名。私钥加密生成数字签名，公钥验证数据及签名。<br>
* 如果数据和签名不匹配则认为验证失败！数字签名的作用就是校验数据在传输过程中不被修改。<br>
* 数字签名，是单向加密的升级！
*
* @author Ice_Liu
*
*/
public class DSACryptUtil {

public static final String ALGORITHM = "DSA";

/**
* 默认密钥字节数
*
* <pre>
*
* DSA
* Default Keysize 1024
* Keysize must be a multiple of 64, ranging from 512 to 1024 (inclusive).
* </pre>
*/
private static final int KEY_SIZE = 1024;

/**
* 默认种子
*/
private static final String DEFAULT_SEED = "0f22507a10bbddd07d8a3082122966e3";

private static final String PUBLIC_KEY = "DSAPublicKey";
private static final String PRIVATE_KEY = "DSAPrivateKey";

/**
* 用私钥对信息生成数字签名
*
* @param data
*            加密数据
* @param privateKey
*            私钥
*
* @return
* @throws Exception
*/
public static String sign(byte[] data, String privateKey) throws Exception {
// 解密由base64编码的私钥
byte[] keyBytes = CryptUtil.decryptBASE64(privateKey);

// 构造PKCS8EncodedKeySpec对象
PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);

// KEY_ALGORITHM 指定的加密算法
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);

// 取私钥匙对象
PrivateKey priKey = keyFactory.generatePrivate(pkcs8KeySpec);

// 用私钥对信息生成数字签名
Signature signature = Signature.getInstance(keyFactory.getAlgorithm());
signature.initSign(priKey);
signature.update(data);

return CryptUtil.encryptBASE64(signature.sign());
}

/**
* 校验数字签名
*
* @param data
*            加密数据
* @param publicKey
*            公钥
* @param sign
*            数字签名
*
* @return 校验成功返回true 失败返回false
* @throws Exception
*
*/
public static boolean verify(byte[] data, String publicKey, String sign) throws Exception {

// 解密由base64编码的公钥
byte[] keyBytes = CryptUtil.decryptBASE64(publicKey);

// 构造X509EncodedKeySpec对象
X509EncodedKeySpec keySpec = new X509EncodedKeySpec(keyBytes);

// ALGORITHM 指定的加密算法
KeyFactory keyFactory = KeyFactory.getInstance(ALGORITHM);

// 取公钥匙对象
PublicKey pubKey = keyFactory.generatePublic(keySpec);

Signature signature = Signature.getInstance(keyFactory.getAlgorithm());
signature.initVerify(pubKey);
signature.update(data);

// 验证签名是否正常
return signature.verify(CryptUtil.decryptBASE64(sign));
}

/**
* 生成密钥
*
* @param seed
*            种子
* @return 密钥对象
* @throws Exception
*/
public static Map<String, Object> initKey(String seed) throws Exception {
KeyPairGenerator keygen = KeyPairGenerator.getInstance(ALGORITHM);
// 初始化随机产生器
SecureRandom secureRandom = new SecureRandom();
secureRandom.setSeed(seed.getBytes());
keygen.initialize(KEY_SIZE, secureRandom);

KeyPair keys = keygen.genKeyPair();

DSAPublicKey publicKey = (DSAPublicKey) keys.getPublic();
DSAPrivateKey privateKey = (DSAPrivateKey) keys.getPrivate();

Map<String, Object> map = new HashMap<String, Object>(2);
map.put(PUBLIC_KEY, publicKey);
map.put(PRIVATE_KEY, privateKey);

return map;
}

/**
* 默认生成密钥
*
* @return 密钥对象
* @throws Exception
*/
public static Map<String, Object> initKey() throws Exception {
return initKey(DEFAULT_SEED);
}

/**
* 取得私钥
*
* @param keyMap
* @return
* @throws Exception
*/
public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {
Key key = (Key) keyMap.get(PRIVATE_KEY);

return CryptUtil.encryptBASE64(key.getEncoded());
}

/**
* 取得公钥
*
* @param keyMap
* @return
* @throws Exception
*/
public static String getPublicKey(Map<String, Object> keyMap) throws Exception {
Key key = (Key) keyMap.get(PUBLIC_KEY);

return CryptUtil.encryptBASE64(key.getEncoded());
}

public static void main(String[] args) {
try {
DHCryptUtil.main(args);
System.out.println("************************************");
System.out.println("DSA 加密与解密");
String inputStr = "abc";
byte[] data = inputStr.getBytes();

// 构建密钥
Map<String, Object> keyMap = DSACryptUtil.initKey();
// 获得密钥
String publicKey = DSACryptUtil.getPublicKey(keyMap);
String privateKey = DSACryptUtil.getPrivateKey(keyMap);

System.err.println("公钥:\r" + publicKey);
System.err.println("私钥:\r" + privateKey);

// 产生签名
String sign = DSACryptUtil.sign(data, privateKey);
System.err.println("签名:\r" + sign);

// 验证签名
boolean status = DSACryptUtil.verify(data, publicKey, sign);
System.err.println("状态:\r" + status);

} catch (Exception e) {
e.printStackTrace();
}

}

}