Java加密技术(六)——数字签名算法DSA

    接下来我们介绍DSA数字签名,非对称加密的另一种实现。
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!


通过java代码实现如下: Coder类见 Java加密技术(一)
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
 * 
 * @author 梁栋
 * @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());
	}
}


再给出一个测试类:
import static org.junit.Assert.*;

import java.util.Map;

import org.junit.Test;

/**
 * 
 * @author 梁栋
 * @version 1.0
 * @since 1.0
 */
public class DSACoderTest {

	@Test
	public void test() 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);
		assertTrue(status);

	}

}

控制台输出:
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:
MC0CFQCMg0J/uZmF8GuRpr3TNq48w60nDwIUJCyYNah+HtbU6NcQfy8Ac6LeLQs=

状态:
true


注意状态为true,就验证成功!



相关链接:
Java加密技术(一)——BASE64与单向加密算法MD5&SHA&MAC
Java加密技术(二)——对称加密DES&AES
Java加密技术(三)——PBE算法
Java加密技术(四)——非对称加密算法RSA
Java加密技术(五)——非对称加密算法的由来
Java加密技术(六)——数字签名算法DSA
Java加密技术(七)——非对称加密算法最高ECC
Java加密技术(八)——数字证书
Java加密技术(九)——初探SSL
Java加密技术(十)——单向认证
Java加密技术(十一)——双向认证
Java加密技术(十二)——*.PFX(*.p12)&个人信息交换文件

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