java数字签名三种方式

以下3钟数字签名都是基于jdk7的
1，RSA

String password="test";
			// 1.初始化密钥
			KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("RSA");
			keyPairGenerator.initialize(512);
			KeyPair keyPair = keyPairGenerator.generateKeyPair();
			RSAPublicKey rsaPublicKey = (RSAPublicKey)keyPair.getPublic();
			RSAPrivateKey rsaPrivateKey = (RSAPrivateKey)keyPair.getPrivate();
			
			// 2.进行签名
			PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(rsaPrivateKey.getEncoded());
			KeyFactory keyFactory = KeyFactory.getInstance("RSA");
			PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
			Signature signature = Signature.getInstance("MD5withRSA");
			signature.initSign(privateKey);
			signature.update(password.getBytes());
			byte[] result = signature.sign();
			//System.out.println("jdk rsa sign:" + Hex.encodeHexString(result) );
			
			// 3.验证签名
			X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(rsaPublicKey.getEncoded());
			keyFactory = KeyFactory.getInstance("RSA");
			PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
			signature = Signature.getInstance("MD5withRSA");
			signature.initVerify(publicKey);
			signature.update(password.getBytes());
			boolean bool = signature.verify(result);

2，DSA

String password="test";
			// 1.初始化密钥
			KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DSA");
			keyPairGenerator.initialize(512);
			KeyPair keyPair = keyPairGenerator.generateKeyPair();
			DSAPublicKey dsaPublicKey = (DSAPublicKey)keyPair.getPublic();
			DSAPrivateKey dsaPrivateKey = (DSAPrivateKey)keyPair.getPrivate();
			
			// 2.进行签名
			PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(dsaPrivateKey.getEncoded());
			KeyFactory keyFactory = KeyFactory.getInstance("DSA");
			PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
			Signature signature = Signature.getInstance("SHA1withDSA");
			signature.initSign(privateKey);
			signature.update(password.getBytes());
			byte[] result = signature.sign();
			System.out.println("jdk dsa sign:" + Hex.encodeHexString(result) );
			
			// 3.验证签名
			X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(dsaPublicKey.getEncoded());
			keyFactory = KeyFactory.getInstance("DSA");
			PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
			signature = Signature.getInstance("SHA1withDSA");
			signature.initVerify(publicKey);
			signature.update(password.getBytes());
			boolean bool = signature.verify(result);

3，ECDSA

String password="test";
			// 1.初始化密钥
			KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("EC");
			keyPairGenerator.initialize(256);
			KeyPair keyPair = keyPairGenerator.generateKeyPair();
			ECPublicKey ecPublicKey = (ECPublicKey)keyPair.getPublic();
			ECPrivateKey ecPrivateKey = (ECPrivateKey)keyPair.getPrivate();
			
			// 2.进行签名
			PKCS8EncodedKeySpec pkcs8EncodedKeySpec = new PKCS8EncodedKeySpec(ecPrivateKey.getEncoded());
			KeyFactory keyFactory = KeyFactory.getInstance("EC");
			PrivateKey privateKey = keyFactory.generatePrivate(pkcs8EncodedKeySpec);
			Signature signature = Signature.getInstance("SHA1withECDSA");
			signature.initSign(privateKey);
			signature.update(password.getBytes());
			byte[] result = signature.sign();
			System.out.println("jdk ecdsa sign:" + Hex.encodeHexString(result) );
			
			// 3.验证签名
			X509EncodedKeySpec x509EncodedKeySpec = new X509EncodedKeySpec(ecPublicKey.getEncoded());
			keyFactory = KeyFactory.getInstance("EC");
			PublicKey publicKey = keyFactory.generatePublic(x509EncodedKeySpec);
			signature = Signature.getInstance("SHA1withECDSA");
			signature.initVerify(publicKey);
			signature.update(password.getBytes());