JAVA加密算法（DSA）

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！也就是说传输中的数据可以不再加密，接收方获得数据后，拿到公钥与签名比对数据是否有效！

通过java代码实现如下：Coder类见 java加密技术（一） 
Java代码

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.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map;   

/**
* DSA安全编码组件
*
*/
public abstract class DSACoder extends Coder {
    /**
     * 可以使用DSA方式获得签名，也可以使用RSA方式获得签名，注意成对儿出现。
     *
     * <code>
     * public static final String KEY_ALGORITHM = "RSA";
     * public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
     * </code>
     **/
    public static final String KEY_ALGORITHM = "DSA";
    public static final String SIGNATURE_ALGORITHM = "DSA";   

    /**
     * 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(KEY_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(SIGNATURE_ALGORITHM);
        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);   

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

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

        Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
        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(KEY_ALGORITHM);
        // 初始化随机产生器
        SecureRandom secureRandom = new SecureRandom();
        secureRandom.setSeed(seed.getBytes());
        keygen.initialize(1024, secureRandom);   

        KeyPair keys = keygen.genKeyPair();   

        PublicKey publicKey = keys.getPublic();
        PrivateKey privateKey = 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.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.spec.PKCS8EncodedKeySpec;
import java.security.spec.X509EncodedKeySpec;
import java.util.HashMap;
import java.util.Map; 

/**
* DSA安全编码组件
*
*/
public abstract class DSACoder extends Coder {
/**
* 可以使用DSA方式获得签名，也可以使用RSA方式获得签名，注意成对儿出现。
*
* <code>
* public static final String KEY_ALGORITHM = "RSA";
* public static final String SIGNATURE_ALGORITHM = "MD5withRSA";
* </code>
**/
public static final String KEY_ALGORITHM = "DSA";
public static final String SIGNATURE_ALGORITHM = "DSA"; 

/**
* 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(KEY_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(SIGNATURE_ALGORITHM);
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); 

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

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

Signature signature = Signature.getInstance(SIGNATURE_ALGORITHM);
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(KEY_ALGORITHM);
// 初始化随机产生器
SecureRandom secureRandom = new SecureRandom();
secureRandom.setSeed(seed.getBytes());
keygen.initialize(1024, secureRandom); 

KeyPair keys = keygen.genKeyPair(); 

PublicKey publicKey = keys.getPublic();
PrivateKey privateKey = 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());
}
} 

不仅可以使用DSA算法，同样也可以使用RSA算法做数字签名，但要注意成对出现：
public static final String KEY_ALGORITHM = "RSA";
public static final String SIGNATURE_ALGORITHM = "MD5withRSA"; 

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

import java.util.Map;   

import org.junit.Test;   

/**
*
*/
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);   

    }   

}  

import static org.junit.Assert.*; 

import java.util.Map; 

import org.junit.Test; 

/**
*
*/
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： 
Console代码 
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

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