RSA自学整理（私匙、公匙加密解密过程）

本文着重叙述私匙、公匙加密解密过程，先上代码
public class CreateSecrteKey {

    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 byte[] decryptBASE64(String key) {
        return Base64.decodeBase64(key);
    }
    public static String encryptBASE64(byte[] bytes) {
        return Base64.encodeBase64String(bytes);
    }
    /**
     * 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));
    }
    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);
    }
    /**
     * 解密

     * 用私钥解密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] decryptByPrivateKey(String data, String key)
            throws Exception {
        return decryptByPrivateKey(decryptBASE64(data),key);
    }
    /**
     * 解密

     * 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
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.DECRYPT_MODE, publicKey);
        return cipher.doFinal(data);
    }
    /**
     * 加密

     * 用公钥加密
     *
     * @param data
     * @param key
     * @return
     * @throws Exception
     */
    public static byte[] encryptByPublicKey(String 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.getBytes());
    }
    /**
     * 加密

     * 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
        Cipher cipher = Cipher.getInstance(keyFactory.getAlgorithm());
        cipher.init(Cipher.ENCRYPT_MODE, privateKey);
        return cipher.doFinal(data);
    }
    /**
     * 取得私钥
     *
     * @param keyMap
     * @return
     * @throws Exception
     */
    public static String getPrivateKey(Map 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 keyMap)
            throws Exception {
        Key key = keyMap.get(PUBLIC_KEY);
        return encryptBASE64(key.getEncoded());
    }
    /**
     * 初始化密钥
     *
     * @return
     * @throws Exception
     */

    public static Map initKey() throws Exception {
        KeyPairGenerator keyPairGen = KeyPairGenerator
                .getInstance(KEY_ALGORITHM);
        keyPairGen.initialize(1024);
        KeyPair keyPair = keyPairGen.generateKeyPair();
        Map keyMap = new HashMap(2);
        keyMap.put(PUBLIC_KEY, keyPair.getPublic());// 公钥
        keyMap.put(PRIVATE_KEY, keyPair.getPrivate());// 私钥
        return keyMap;
    }
    public static void main(String[] args) {
        Map keyMap;
        try {
            keyMap = initKey();
            String publicKey = getPublicKey(keyMap);
            System.out.println(publicKey);
            byte[] shilis = encryptByPublicKey("shili", publicKey);
            String privateKey = getPrivateKey(keyMap);
            System.out.println(privateKey);
            byte[] bytes = decryptByPrivateKey(shilis, privateKey);
            String s = bytetoString(bytes);
            System.out.println(s);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    /**
     * 字节数组转为普通字符串（ASCII对应的字符）
     *
     * @param bytearray
     *            byte[]
     * @return String
     */
    public static String bytetoString(byte[] bytearray) {
        String result = "";
        char temp;

        int length = bytearray.length;
        for (int i = 0; i < length; i++) {
            temp = (char) bytearray[i];
            result += temp;
        }
        return result;
    }
}

代码直接copy，启动main方法，可以看到公匙加密以及私匙解密的过程。

私匙加密，公匙解密

public static void main(String[] args) {

Map keyMap;
try {
    keyMap = initKey();
    String publicKey = getPublicKey(keyMap);
    System.out.println(publicKey);
    String privateKey = getPrivateKey(keyMap);
    System.out.println(privateKey);
    String strs= "zifuchuan";
    byte[] bytes2 = strs.getBytes();
    byte[] bytes = encryptByPrivateKey(bytes2, privateKey);
    byte[] bytes1 = decryptByPublicKey(bytes, publicKey);
    String s = bytetoString(bytes1);
    System.out.println(s);
} catch (Exception e) {
    e.printStackTrace();
}

}

数字签名生成及校验

public static void main(String[] args) {
    Map keyMap;
    try {
        keyMap = initKey();
        String publicKey = getPublicKey(keyMap);
        System.out.println(publicKey);
        String privateKey = getPrivateKey(keyMap);
        System.out.println(privateKey);
        String strs= "zifuchuan";
        byte[] bytes2 = strs.getBytes();
        String sign = sign(bytes2, privateKey);
        boolean verify = verify(bytes2, publicKey, sign);
        System.out.println(verify);
    } catch (Exception e) {
        e.printStackTrace();
    }
}