CRYPTO

• Intro #

  常见的 对称加密 算法主要有 DES、3DES、 AES 等，常见的 非对称算法 主要有 RSA、DSA、ECC，散列算法 主要有 SHA-1、 MD5 等。 代码实现参考

• Key #

  • 生成自定义key #

    使用ascii生成可以的方法如下：

    public static byte[] getRandomKey(){
        int len = 16; // 128 ->16  256->32
        byte[] keys = new byte[len];
        Random rdom = new Random();
        for (int i = 0; i < len; i++) {
            keys[i] = (byte) (rdom.nextInt(126-34) +34);
        }
        return keys;
    }
    // kZZ`MbMLbp5sc7Y'
    // U2yT4Q)2Ss+Li=Y)
    // "OAKJH5kKKLq?g'p
    // h&GKS.gAG,H_@et%
    // .]?]_8ECB[Z'gYn)
    // <mJ\J_PlLE][_uI9
    // 2j=HC,#Au}VDE\P:
    // 27Fqc/j6LODd<.8O
    // Gtt17Q\IyFrNtthk
    // 4q>?A{b|mo@kqM2Q
    

    

  • 使用SecretKeyFactory构造 #

    private static SecretKey getKey(String key) throws Exception {
        DESKeySpec dks = new DESKeySpec(key.getBytes("utf-8"));
        SecretKeyFactory keyFactory = SecretKeyFactory.getInstance("DES");
        return keyFactory.generateSecret(dks);
    }
    // split .can direct use
    private static SecretKey getKey(byte[] key){
        return new SecretKeySpec(key, "AES");
    }
    

  • 使用KeyGenerator生成全新的 #

    public static byte[] getRandomKey() throws Exception {
        KeyGenerator keyGenerator = KeyGenerator.getInstance("AES");
        SecureRandom secureRandom = SecureRandom.getInstance("SHA1PRNG", "SUN");
        secureRandom.setSeed(("AES/CBC/PKCS7Padding" + "EVERY-seed").getBytes());
        keyGenerator.init(256, secureRandom); //要生成多少位，只需要修改这里即可128, 192或256
        SecretKey originalKey = keyGenerator.generateKey();
        return originalKey.getEncoded(); // byte[32]
    }
    

  • Reference

    • https://stackoverflow.com/questions/26295437/should-i-use-keygenerator-or-secretkeyfactory
    • https://www.johndcook.com/blog/2022/05/28/how-to-memorize-the-ascii-table/

• Test #

  • DES #

    @Test
    public void testDES(){
    
        String key = "U2yT4Q)2Ss+Li=Y)";
        String iv  = "2j=HC,#Au}VDE\\P:";
        iv  = "2=H,#Au}"; //des 8 byte
        String data = "hello world from 加密";
    
        String encrypt = DES.encrypt(data, key.getBytes(), iv.getBytes());
        System.out.println(encrypt);
        String decrypt = DES.decrypt(encrypt, key.getBytes(), iv.getBytes());
        System.out.println(decrypt);
    
    }
    

    

  • AES #

    @Test
    public void testAES(){
        String key = "U2yT4Q)2Ss+Li=Y)";
        String iv  = "2j=HC,#Au}VDE\\P:";
        //iv  = "2=H,#Au}"; //des 8 byte
        String data = "hello world from 加密";
    
        String encrypt = AES.encrypt(data, key.getBytes(), iv.getBytes());
        System.out.println(encrypt);
        String decrypt = AES.decrypt(encrypt, key.getBytes(), iv.getBytes());
        System.out.println(decrypt);
    }
    

    

• Reference #

  • https://juejin.cn/post/6844903638117122056
  • https://stackoverflow.com/questions/140131/convert-a-string-representation-of-a-hex-dump-to-a-byte-array-using-java
  • Wrong key size
  • Wrong IV length: must be 8 bytes long