接下来我们介绍DSA数字签名，非对称加密的另一种实现。
[b]DSA[/b]
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！ :D
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通过java代码实现如下：[b]Coder类见 [url=http://snowolf.iteye.com/blog/379860]Java加密技术（一）[/url][/b]
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: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私钥:MIIBTAIBADCCASwGByqGSM44BAEwggEfAoGBAP1/U4EddRIpUt9KnC7s5Of2EbdSPO9EAMMeP4C2USZpRV1AIlH7WT2NWPq/xfW6MPbLm1Vs14E7gB00b/JmYLdrmVClpJ+f6AR7ECLCT7up1/63xhv4O1fnxqimFQ8E+4P208UewwI1VBNaFpEy9nXzrith1yrv8iIDGZ3RSAHHAhUAl2BQjxUjC8yykrmCouuEC/BYHPUCgYEA9+GghdabPd7LvKtcNrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJFnEj6EwoFhO3zwkyjMim4TwWeotUfI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImog9/hWuWfBpKLZl6Ae1UlZAFMO/7PSSoEFwIVAIegLUtmm2oQKQJTOiLugHTSjl/q签名:MC0CFQCMg0J/uZmF8GuRpr3TNq48w60nDwIUJCyYNah+HtbU6NcQfy8Ac6LeLQs=状态:true
注意状态为true，就验证成功！ :D
[b]
相关链接：
[url=http://snowolf.iteye.com/blog/379860]Java加密技术（一）——BASE64与单向加密算法MD5&SHA&MAC[/url]
[url=http://snowolf.iteye.com/blog/380034]Java加密技术（二）——对称加密DES&AES[/url]
[url=http://snowolf.iteye.com/blog/380761]Java加密技术（三）——PBE算法[/url]
[url=http://snowolf.iteye.com/blog/381767]Java加密技术（四）——非对称加密算法RSA[/url]
[url=http://snowolf.iteye.com/blog/382422]Java加密技术（五）——非对称加密算法的由来[/url]
[url=http://snowolf.iteye.com/blog/382749]Java加密技术（六）——数字签名算法DSA[/url]
[url=http://snowolf.iteye.com/blog/383412]Java加密技术（七）——非对称加密算法最高ECC[/url]
[url=http://snowolf.iteye.com/blog/391931]Java加密技术（八）——数字证书[/url]
[url=http://snowolf.iteye.com/blog/397693]Java加密技术（九）——初探SSL[/url]
[url=http://snowolf.iteye.com/blog/398198]Java加密技术（十）——单向认证[/url]
[url=http://snowolf.iteye.com/blog/510985]Java加密技术（十一）——双向认证[/url]
[url=http://snowolf.iteye.com/blog/735294]Java加密技术（十二）——*.PFX(*.p12)&个人信息交换文件[/url]
[/b]
相关资源：敏捷开发V1.0.pptx
