Java加密与解密

Base64

Base64是网络上最常见的用于传输8Bit(1Byte)字节码的编码方式之一，Base64就是一种基于64个可打印字符来表示二进制数据的方法。Base64编码变长，具有不可读性。其实Base64是一种编码方式而不是加密方式。 

public class Base64 implements Encryption, Decryption {

    private static Base64 instance;

    private Base64() {
    }

    public static synchronized Base64 getInstance() {
        return instance == null ? new Base64() : instance;
    }

    @Override
    public byte[] encrypt(byte[] src) {
        return java.util.Base64.getEncoder().encode(src);
    }

    @Override
    public byte[] decrypt(byte[] src) {
        return java.util.Base64.getDecoder().decode(src);
    }
}

MD5

MD5即Message-Digest Algorithm 5（信息-摘要算法5），用于确保信息传输完整一致。是计算机广泛使用的杂凑算法之一（又译摘要算法、哈希算法），主流编程语言普遍已有MD5实现。将数据（如汉字）运算为另一固定长度值，是杂凑算法的基础原理。

public class Md5 implements Encryption {

    private static Md5 instance;

    private Md5() {
    }

    public static synchronized Md5 getInstance() {
        return instance == null ? new Md5() : instance;
    }

    @Override
    public byte[] encrypt(byte[] src) {
        MessageDigest md;
        byte[] result;
        try {
            md = MessageDigest.getInstance(Algorithm.MD5.value());
            md.update(src);
            result = md.digest();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("No such algorithm: " + Algorithm.MD5.value());
        }
        return result;
    }
}

Sha1

安全哈希算法（Secure Hash Algorithm）主要适用于数字签名标准（Digital Signature Standard DSS）里面定义的数字签名算法（Digital Signature Algorithm DSA）。对于长度小于2^64位的消息，SHA1会产生一个160位的消息摘要。该算法的思想是接收一段明文，然后以一种不可逆的方式将它转换成一段（通常更小）密文，散列函数值可以说是对明文的一种“指纹”或是“摘要”所以对散列值的数字签名就可以视为对此明文的数字签名。

public class Sha implements Encryption {

    private static Sha instance;

    private Sha() {
    }

    public static synchronized Sha getInstance() {
        return instance == null ? new Sha() : instance;
    }

    @Override
    public byte[] encrypt(byte[] src) {
        MessageDigest md;
        byte[] result;
        try {
            md = MessageDigest.getInstance(Algorithm.SHA.value());
            md.update(src);
            result = md.digest();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("No such algorithm: " + Algorithm.SHA.value());
        }
        return result;
    }
}

Pbe

PBE算法（Password Based Encryption，基于口令加密）是一种基于口令的加密算法，其特点是使用口令代替了密钥，而口令由用户自己掌管，采用随机数杂凑多重加密等方法保证数据的安全性。

public class Pbe implements Encryption, Decryption {

    /**
     * define the iteration count: 1000<br>
     */
    private static final int ITERATION_COUNT = 1000;

    /**
     * define the PBE password<br>
     */
    private static final String PBE_PASSWORD = "enfldsgbnlsngdlksdsgm";

    /**
     * define the salt<br>
     */
    private static final byte[] SALT = { (byte) 0xde, (byte) 0x33, (byte) 0x10, (byte) 0x12, (byte) 0xde, (byte) 0x33,
            (byte) 0x10, (byte) 0x12, };

    private static Pbe instance;

    private Pbe() {
    }

    public static synchronized Pbe getInstance() {
        return instance == null ? new Pbe() : instance;
    }

    @Override
    public byte[] encrypt(byte[] src) {
        Key key = getPBEKey();
        PBEParameterSpec parameterSpec = new PBEParameterSpec(SALT, ITERATION_COUNT);
        Cipher cipher;
        byte[] result;
        try {
            cipher = Cipher.getInstance(Algorithm.PBE.value());
            cipher.init(Cipher.ENCRYPT_MODE, key, parameterSpec);
            result = cipher.doFinal(src);
        } catch (Exception e) {
            throw new RuntimeException("Encrypt failed.");
        }

        return result;
    }

    @Override
    public byte[] decrypt(byte[] src) {
        Key key = getPBEKey();
        PBEParameterSpec parameterSpec = new PBEParameterSpec(SALT, ITERATION_COUNT);
        Cipher cipher;
        byte[] result;
        try {
            cipher = Cipher.getInstance(Algorithm.PBE.value());
            cipher.init(Cipher.DECRYPT_MODE, key, parameterSpec);
            result = cipher.doFinal(src);
        } catch (Exception e) {
            throw new RuntimeException("Decrypt failed.");
        }

        return result;
    }

    /**
     * Generate a PBE secret key according to the PBE password.<br>
     * 
     * @return
     */
    private static Key getPBEKey() {
        SecretKeyFactory keyFactory;
        SecretKey secretKey;
        try {
            keyFactory = SecretKeyFactory.getInstance(Algorithm.PBE.value());
            PBEKeySpec keySpec = new PBEKeySpec(PBE_PASSWORD.toCharArray());
            secretKey = keyFactory.generateSecret(keySpec);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("No such algorithm: " + Algorithm.PBE.value());
        } catch (InvalidKeySpecException e) {
            throw new RuntimeException("The key is Invalid.");
        }

        return secretKey;
    }
}

Hmac

HMAC是密钥相关的哈希运算消息认证码，HMAC运算利用哈希算法，以一个密钥和一个消息为输入，生成一个消息摘要作为输出。HMAC是密钥相关的哈希运算消息认证码，HMAC运算利用哈希算法，以一个密钥和一个消息为输入，生成一个消息摘要作为输出。

public class Hmac implements Encryption {

    private static Hmac instance;

    private static byte[] macKey;

    private Hmac() {
    }

    public static synchronized Hmac getInstance() {
        if (instance == null) {
            macKey = initMacKey();
            instance = new Hmac();
        }

        return instance;
    }

    @Override
    public byte[] encrypt(byte[] src) {
        SecretKey secretKey = new SecretKeySpec(macKey, Algorithm.HMAC.value());
        Mac mac;
        byte[] result;
        try {
            mac = Mac.getInstance(secretKey.getAlgorithm());
            mac.init(secretKey);
            result = mac.doFinal(src);
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("No such algorithm: " + secretKey.getAlgorithm());
        } catch (InvalidKeyException e) {
            throw new RuntimeException("The key is Invalid.");
        }

        return result;
    }

    /**
     * Generate a MAC secret key.<br>
     * 
     * @return MAC key
     */
    private static byte[] initMacKey() {
        KeyGenerator keyGenerator;
        Key result;
        try {
            keyGenerator = KeyGenerator.getInstance(Algorithm.HMAC.value());
            result = keyGenerator.generateKey();
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException("No such algorithm: " + Algorithm.HMAC.value());
        }
        return result.getEncoded();
    }
}

[其他代码]

public enum Algorithm {

    BASE64("BASE64"), MD5("MD5"), SHA("SHA"), HMAC("HmacMD5"), PBE("PBEWITHMD5ANDDES");

    private String value;

    private Algorithm(String value) {
        this.value = value;
    }

    public String value() {
        return value;
    }
}

public interface Decryption {
    byte[] decrypt(byte[] src);
}

public interface Encryption {
    byte[] encrypt(byte[] src);
}