JAVA加密算法（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！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