数字签名算法

package com.kaishengit.security;
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.Signature;  
import java.security.interfaces.RSAPrivateKey;  
import java.security.interfaces.RSAPublicKey;  
import java.security.spec.PKCS8EncodedKeySpec;  
import java.security.spec.X509EncodedKeySpec;  
import java.util.HashMap;  
import java.util.Map;  
  

import javax.crypto.Cipher;  

import org.apache.commons.codec.binary.Base64;
  
public class RSACoder {  
    public static final String KEY_ALGORITHM = "RSA";  
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";  
    private static final String PUBLIC_KEY = "RSAPublicKey";  
    private static final String PRIVATE_KEY = "RSAPrivateKey";  
  
    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());  
    }  
  
    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));  
    }  
  
    public static byte[] decryptByPrivateKey(byte[] data, String key) throws Exception {  
        // 对密钥解密  
        byte[] keyBytes = decryptBASE64(key);  
        // 取得私钥  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);  
        // 对数据解密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.DECRYPT_MODE, privateKey);  
        return cipher.doFinal(data);  
    }  
  
    public static byte[] decryptByPublicKey(byte[] data, String key) throws Exception {  
        // 对密钥解密  
        byte[] keyBytes = decryptBASE64(key);  
        // 取得公钥  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key publicKey = keyFactory.generatePublic(x509KeySpec);  
        // 对数据解密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.DECRYPT_MODE, publicKey);  
        return cipher.doFinal(data);  
    }  
  
    public static byte[] encryptByPublicKey(byte[] data, String key) throws Exception {  
        // 对公钥解密  
        byte[] keyBytes = decryptBASE64(key);  
        // 取得公钥  
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key publicKey = keyFactory.generatePublic(x509KeySpec);  
        // 对数据加密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.ENCRYPT_MODE, publicKey);  
        return cipher.doFinal(data);  
    }  
  
    public static byte[] encryptByPrivateKey(byte[] data, String key) throws Exception {  
        // 对密钥解密  
        byte[] keyBytes = decryptBASE64(key);  
        // 取得私钥  
        PKCS8EncodedKeySpec pkcs8KeySpec = new PKCS8EncodedKeySpec(keyBytes);  
        KeyFactory keyFactory = KeyFactory.getInstance(KEY_ALGORITHM);  
        Key privateKey = keyFactory.generatePrivate(pkcs8KeySpec);  
        // 对数据加密  
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());  
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);  
        return cipher.doFinal(data);  
    }  
  
    private static byte[] decryptBASE64(String key) throws Exception {  
        // TODO Auto-generated method stub  
        //return Base64Utill.decodeBase64(key);  
        return Base64.decodeBase64(key);
    }  
  
    public static String getPrivateKey(Map<String, Object> keyMap) throws Exception {  
        Key key = (Key) keyMap.get(PRIVATE_KEY);  
        return encryptBASE64(key.getEncoded());  
    }  
  
    private static String encryptBASE64(byte[] encoded) throws Exception {  
        // TODO Auto-generated method stub  
//        return Base64Utill.encodeBase64(encoded); 
        return Base64.encodeBase64String(encoded);
    }  
  
    public static String getPublicKey(Map<String, Object> keyMap) throws Exception {  
        Key key = (Key) keyMap.get(PUBLIC_KEY);  
        return encryptBASE64(key.getEncoded());  
    }  
  
    public static Map<String, Object> initKey() throws Exception {  
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);  
        keyPairGen.initialize(1024);  
        KeyPair keyPair = keyPairGen.generateKeyPair();  
        // 公钥  
        RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();  
        // 私钥  
        RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();  
        Map<String, Object> keyMap = new HashMap<String, Object>(2);  
        keyMap.put(PUBLIC_KEY, publicKey);  
        keyMap.put(PRIVATE_KEY, privateKey);  
        return keyMap;  
    }  
  
    public static void testEncode(String publicKey, String privateKey) throws Exception {  
        System.err.println("公钥加密——私钥解密");  
        String inputStr = "abc";  
        byte[] data = inputStr.getBytes();  
        byte[] encodedData = RSACoder.encryptByPublicKey(data, publicKey);  
        byte[] decodedData = RSACoder.decryptByPrivateKey(encodedData, privateKey);  
        String outputStr = new String(decodedData);  
        System.err.println("加密前: " + inputStr);  
        System.err.println("加密后：" + Base64.encodeBase64String(encodedData));  
        System.err.println("解密后：" + outputStr);  
        System.err.println(inputStr.equals(outputStr));  
    }  
  
    public static void testSign(String publicKey, String privateKey) throws Exception {  
        System.err.println("私钥加密——公钥解密");  
        String inputStr = "sign";  
        byte[] data = inputStr.getBytes();  
        byte[] encodedData = RSACoder.encryptByPrivateKey(data, privateKey);  
        byte[] decodedData = RSACoder.decryptByPublicKey(encodedData, publicKey);  
        String outputStr = new String(decodedData);  
        System.err.println("加密前: " + inputStr + "==" + "解密后: " + outputStr);  
        System.err.println(inputStr.equals(outputStr));  
        System.err.println("私钥签名——公钥验证签名");  
        // 产生签名  
        String sign = RSACoder.sign(encodedData, privateKey);  
        System.err.println("签名:" + sign);  
        // 验证签名  
        boolean status = RSACoder.verify(encodedData, publicKey, sign);  
        System.err.println("状态:" + status);  
    }  
  
    public static void main(String[] rags) throws Exception {  
        Map<String, Object> keyMap = RSACoder.initKey();  
        String publicKey = RSACoder.getPublicKey(keyMap);  
        String privateKey = RSACoder.getPrivateKey(keyMap);  
        System.err.println("公钥: nr" + publicKey);  
        System.err.println("私钥： nr" + privateKey);  
        //testEncode(publicKey, privateKey);  
        testSign(publicKey, privateKey);  
  
    }  
  
}

这些是抄人家代码的