非对称加密RSA

本文转载自：http://snowolf.iteye.com/blog/381767

RSA
    这种算法1978年就出现了，它是第一个既能用于数据加密也能用于数字签名的算法。它易于理解和操作，也很流行。算法的名字以发明者的名字命名：Ron Rivest, AdiShamir 和Leonard Adleman。
    这种加密算法的特点主要是密钥的变化，上文我们看到DES只有一个密钥。相当于只有一把钥匙，如果这把钥匙丢了，数据也就不安全了。RSA同时有两把钥 匙，公钥与私钥。同时支持数字签名。数字签名的意义在于，对传输过来的数据进行校验。确保数据在传输工程中不被修改。

流程分析：

1. 甲方构建密钥对儿，将公钥公布给乙方，将私钥保留。
2. 甲方使用私钥加密数据，然后用私钥对加密后的数据签名，发送给乙方签名以及加密后的数据；乙方使用公钥、签名来验证待解密数据是否有效，如果有效使用公钥对数据解密。
3. 乙方使用公钥加密数据，向甲方发送经过加密后的数据；甲方获得加密数据，通过私钥解密。

按如上步骤给出序列图，如下：

1. 
2. 
3. 

通过java代码实现如下：

package com.java.security;
import java.io.ByteArrayOutputStream;
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;

/**
 * RSA安全编码组件
 * 
 */
public abstract class RSAUtils extends EncryptUtils {
    public static final String KEY_ALGORITHM = "RSA";
    public static final String SIGNATURE_ALGORITHM = "MD5withRSA";//也可以是　SHA1withRSA
    private  static final int  KEYSIZE = 1024;//单位：bit
    //加密1byte的明文,需要至少1+11=12bytes的密钥
    private  static final int  MAX_DECRYPT_BLOCK = KEYSIZE / 8;//密钥长度
    private  static final int  MAX_ENCRYPT_BLOCK = MAX_DECRYPT_BLOCK - 11;//RSA最大加密明文大小
    private static final String PUBLIC_KEY = "RSAPublicKey";
    private static final String PRIVATE_KEY = "RSAPrivateKey";

    /**
     * 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));
    }

    /**
     * 解密<br>
     * 用私钥解密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    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
        byte[] result = decrypt(data,privateKey);

        return result;
    }

    /**
     * 解密<br>
     * 用公钥解密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    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
        byte[] result = decrypt(data,publicKey);

        return result;
    }

    /**
     * 加密<br>
     * 用公钥加密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    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
        byte[] result = encrypt(data, publicKey);
        return result;
    }

    /**
     * 加密<br>
     * 用私钥加密
     * 
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    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
        byte[] result = encrypt(data, privateKey);
        return result;
    }
    /**
     * 加密
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
     public static byte[] encrypt(byte[] data, Key key) throws Exception {
            Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
            cipher.init(Cipher.ENCRYPT_MODE, key);
            int inputLen = data.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_ENCRYPT_BLOCK) {
                    cache = cipher.doFinal(data, offSet, MAX_ENCRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(data, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_ENCRYPT_BLOCK;
            }
            byte[] encryptedData = out.toByteArray();
            out.close();
            return encryptedData;
        }
      /**
         * 解密
         * @param data
         * @param key
         * @return
         * @throws Exception
         */
     public static byte[] decrypt(byte[] data, Key key) throws Exception {
            Cipher cipher = Cipher.getInstance(KEY_ALGORITHM);
            cipher.init(Cipher.DECRYPT_MODE, key);
            int inputLen = data.length;
            ByteArrayOutputStream out = new ByteArrayOutputStream();
            int offSet = 0;
            byte[] cache;
            int i = 0;
            while (inputLen - offSet > 0) {
                if (inputLen - offSet > MAX_DECRYPT_BLOCK) {
                    cache = cipher.doFinal(data, offSet, MAX_DECRYPT_BLOCK);
                } else {
                    cache = cipher.doFinal(data, offSet, inputLen - offSet);
                }
                out.write(cache, 0, cache.length);
                i++;
                offSet = i * MAX_DECRYPT_BLOCK;
            }
            byte[] decryptedData = out.toByteArray();
            out.close();
            return decryptedData;
        }
    /**
     * 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());
    }

    /**
     * 初始化密钥
     * 
     * @return
     * @throws Exception
     */
    public static Map<String, Object> initKey() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(KEYSIZE);
        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 main(String[] args) throws Exception{
        testSign();
    }
    
    public static void testEncrypt() throws Exception {  
        
        Map<String, Object> keyMap = initKey();  
        
        String publicKey = getPublicKey(keyMap); 
        
        String privateKey = getPrivateKey(keyMap);  
        
        System.err.println("公钥: \n\r" + publicKey);  
        
        System.err.println("私钥： \n\r" + privateKey); 
        
        System.err.println("公钥加密——私钥解密");  
        
        //加密数据超过117byte 验证是否通过
        String inputStr = "abcdefghigklmnopkrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ0123456789abcdefghigklmnopkrstuvwxyzABCDEFGHIGKLMNOPQRSTUVWXYZ0123456789";  
        
        byte[] data = inputStr.getBytes();  
  
        byte[] encodedData = encryptByPublicKey(data, publicKey);  
  
        byte[] decodedData = decryptByPrivateKey(encodedData,privateKey);  
  
        String outputStr = new String(decodedData);  
        
        System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);  
    }
    
    public static void testSign() throws Exception {  
        
        Map<String, Object> keyMap = initKey();  
        
        String publicKey = getPublicKey(keyMap);  
        
        String privateKey = getPrivateKey(keyMap);  
        
        System.err.println("私钥加密——公钥解密");  
        
        String inputStr = "sign";  
        
        byte[] data = inputStr.getBytes();  
  
        byte[] encodedData = encryptByPrivateKey(data, privateKey);  
  
        byte[] decodedData = decryptByPublicKey(encodedData, publicKey);  
  
        String outputStr = new String(decodedData);  
        
        System.err.println("加密前: " + inputStr + "\n\r" + "解密后: " + outputStr);  
  
        System.err.println("私钥签名——公钥验证签名");  
        // 产生签名  
        String sign = sign(encodedData, privateKey); 

        System.err.println("签名:\r" + sign);  
  
        // 验证签名  
        boolean status = verify(encodedData, publicKey, sign);
        
        System.err.println("状态:\r" + status);  
  
    }  
}