Android中常用的加密方式[通俗易懂]

public static String getSignUtil(String key ,String base) {
    Log.i(TAG, "getSignUtil: GET SIGN");
    String type = "HmacSHA1";
    SecretKeySpec secret = new SecretKeySpec(key.getBytes(), type);
    Mac mac = null;
    try {
        mac = Mac.getInstance(type);
        mac.init(secret);
        byte[] digest = mac.doFinal(base.getBytes());
        Log.i(TAG, "authorization:  " + Base64.encodeToString(digest, Base64.DEFAULT));
        return Base64.encodeToString(digest, Base64.DEFAULT);
    } catch (Exception e) {
        Log.e(TAG, "getSignUtil: " + e.toString());
    }
    return type;
}

public static String md5(String input) {
    byte[] bytes = new byte[0];
    try {
        bytes = MessageDigest.getInstance("MD5").digest(input.getBytes());
    } catch (NoSuchAlgorithmException e) {
        Log.e(TAG, "md5: " + e.toString());
    }
    return printHexBinary(bytes);
}

public static String printHexBinary(byte[] data) {
    StringBuilder r = new StringBuilder(data.length * 2);
    for (byte b : data) {
        r.append(hexCode[(b >> 4) & 0xF]);
        r.append(hexCode[(b & 0xF)]);
    }
    return r.toString();
}


/**
 * RSA私钥解密
 *
 * @param message    加密字符串
 * @param privateKey 私钥
 * @return铭文
 */

public static String decrypt(String message, String privateKey) {
    try {
        if (message.contains(" ")) {
            message = message.replaceAll(" " , "+");
        }
        //base64编码的私钥
        final byte[] decoded = Base64.decode(privateKey, Base64.DEFAULT);

        //final byte[] inputByte = Base64.decodeBase64(message.getBytes(StandardCharsets.UTF_8))

        //decodeBase64(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
        Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        //64位解码加密后的字符串
        final byte[] inputByte = Base64.decode(message.getBytes(StandardCharsets.UTF_8), Base64.DEFAULT);

        //  decodeBase64(message.getBytes(StandardCharsets.UTF_8));
        //密文
        final int len = inputByte.length;
        //偏移量
        int offset = 0;
        //段数
        int i = 0;
        final ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while (len - offset > 0) {
            byte[] cache;
            if
            (len - offset > 128) {
                cache = cipher.doFinal(inputByte, offset, 128);
            } else {
                cache = cipher.doFinal(inputByte, offset, len - offset);
            }
            bos.write(cache);
            i++;
            offset = 128 * i;
        }
        bos.close();
        return new String(bos.toByteArray(), StandardCharsets.UTF_8);
    } catch (InvalidKeyException | InvalidKeySpecException | NoSuchAlgorithmException | NoSuchPaddingException
            | IllegalBlockSizeException | BadPaddingException | IOException e) {
        Log.e(TAG, String.format("decrypt: 数据解密异常 , 原始数据： %s，密钥： %s，e: %s " , message, privateKey, e));
    }
    return null;
}




/**
 * RSA私钥解密
 *
 * @param message    加密字符串
 * @param privateKey 私钥
 * @return 铭文
 */

public static String decrypt2(String message, String privateKey) {
    try {
        if (message.contains(" ")) {
            message = message.replaceAll(" ", "+");
        }
        //base64编码的私钥
        final byte[] decoded = Base64.decode(privateKey.getBytes(StandardCharsets.UTF_8),0);


      //  final byte[] decoded = Base64Utils.decode(privateKey);
        RSAPrivateKey priKey = (RSAPrivateKey) KeyFactory.getInstance("RSA").generatePrivate(new PKCS8EncodedKeySpec(decoded));
        Cipher cipher = Cipher.getInstance("RSA");
        cipher.init(Cipher.DECRYPT_MODE, priKey);
        //64位解码加密后的字符串
        final byte[] inputByte = Base64.decode(message.getBytes(StandardCharsets.UTF_8),0);
        //密文
        final int len = inputByte.length;
        //偏移量
        int offset = 0;
        //段数
        int i = 0;
        final ByteArrayOutputStream bos = new ByteArrayOutputStream();
        while (len - offset > 0) {
            byte[] cache;
            if (len - offset > 128) {
                cache = cipher.doFinal(inputByte, offset, 128);
            } else {
                cache = cipher.doFinal(inputByte, offset, len - offset);
            }
            bos.write(cache);
            i++;
            offset = 128 * i;
        }
        bos.close();

        return new String(bos.toByteArray(),StandardCharsets.UTF_8);
    } catch (InvalidKeyException | InvalidKeySpecException | NoSuchAlgorithmException
            | NoSuchPaddingException | IllegalBlockSizeException | BadPaddingException | IOException e) {
        Log.e(TAG, String.format("decrypt: 数据解密异常 , 原始数据： %s，密钥： %s，e: %s " , message, privateKey, e));
    }
    return null;
}