24、Java加密技术（六）——数字签名算法DSA

<转>http://snowolf.iteye.com/blog/382749
DSA
DSA-Digital Signature Algorithm 是Schnorr和ElGamal签名算法的变种，被美国NIST作为DSS(DigitalSignature Standard)。简单的说，这是一种更高级的验证方式，用作数字签名。不单只有公钥、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。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。数字签名，是单向加密的升级。

package org.nick.encrypt;

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安全编码组件 
 * @version 1.0 
 * @since 1.0 
 */  
public abstract class DSACoder extends Coder {  
  
    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 = 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 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 = 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(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 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 encryptBASE64(key.getEncoded());  
    }  
}  

import java.math.BigInteger;
import java.util.Map;

import org.nick.encrypt.Coder;
import org.nick.encrypt.DESCoder;
import org.nick.encrypt.DHCoder;
import org.nick.encrypt.DSACoder;
import org.nick.encrypt.PBECoder;
import org.nick.encrypt.RSACoder;
public class Test
{
   
    public static void main(String[] str) throws Exception {  
        String inputStr = "abc";  
        byte[] data = inputStr.getBytes();  
  
        // 构建密钥  
        Map<String, Object> keyMap = DSACoder.initKey();  
  
        // 获得密钥  
        String publicKey = DSACoder.getPublicKey(keyMap);  
        String privateKey = DSACoder.getPrivateKey(keyMap);  
  
        System.err.println("公钥:\r" + publicKey);  
        System.err.println("私钥:\r" + privateKey);  
  
        // 产生签名  
        String sign = DSACoder.sign(data, privateKey);  
        System.err.println("签名:\r" + sign);  
  
        // 验证签名  
        boolean status = DSACoder.verify(data, publicKey, sign);  
        System.err.println("状态:\r" + status);  
    }
}

公钥:
MIIBtzCCASwGByqGSM44BAEwggEfAoGBAP1/U4EddRIpUt9KnC7s5Of2EbdSPO9EAMMeP4C2USZp
RV1AIlH7WT2NWPq/xfW6MPbLm1Vs14E7gB00b/JmYLdrmVClpJ+f6AR7ECLCT7up1/63xhv4O1fn
xqimFQ8E+4P208UewwI1VBNaFpEy9nXzrith1yrv8iIDGZ3RSAHHAhUAl2BQjxUjC8yykrmCouuE
C/BYHPUCgYEA9+GghdabPd7LvKtcNrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJ
FnEj6EwoFhO3zwkyjMim4TwWeotUfI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImo
g9/hWuWfBpKLZl6Ae1UlZAFMO/7PSSoDgYQAAoGAIu4RUlcQLp49PI0MrbssOY+3uySVnp0TULSv
5T4VaHoKzsLHgGTrwOvsGA+V3yCNl2WDu3D84bSLF7liTWgOj+SMOEaPk4VyRTlLXZWGPsf1Mfd9
21XAbMeVyKDSHHVGbMjBScajf3bXooYQMlyoHiOt/WrCo+mv7efstMM0PGo=

私钥:
MIIBTAIBADCCASwGByqGSM44BAEwggEfAoGBAP1/U4EddRIpUt9KnC7s5Of2EbdSPO9EAMMeP4C2
USZpRV1AIlH7WT2NWPq/xfW6MPbLm1Vs14E7gB00b/JmYLdrmVClpJ+f6AR7ECLCT7up1/63xhv4
O1fnxqimFQ8E+4P208UewwI1VBNaFpEy9nXzrith1yrv8iIDGZ3RSAHHAhUAl2BQjxUjC8yykrmC
ouuEC/BYHPUCgYEA9+GghdabPd7LvKtcNrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCB
gLRJFnEj6EwoFhO3zwkyjMim4TwWeotUfI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhR
kImog9/hWuWfBpKLZl6Ae1UlZAFMO/7PSSoEFwIVAIegLUtmm2oQKQJTOiLugHTSjl/q

签名:
MCwCFGChMYA6jAhUapgLwd/G7vy9GK82AhRSVx+cuzm3eSklfr9nNh9CjMlMyg==

状态:
true
验证成功。