JAVA implements AES encryption

Last time I introduced itJAVA implements AES encryption》, mentioned that DES is less and less used in recent years, because it uses 56-bit keys, which are easier to crack. In recent years, it has gradually been replaced by AES, and AES has become one of the most popular algorithms in symmetric encryption at present; AES can use 128, 192, and 256-bit keys, and encrypt and decrypt data with 128-bit packets. This article briefly introduces how to implement AES encryption through JAVA.

A little gossip, skimming the principles and algorithms of AES encryption, search for professional websites directly, let’s take a look at the specific implementation of JAVA.

The code has a detailed explanation, no nonsense.

/** * 加密 * * @param content 需要加密的内容 * @param password 加密密码 * @return */ public static byte[] encrypt(String content, String password) { try { KeyGenerator kgen = ("AES"); (128, new SecureRandom(())); SecretKey secretKey = (); byte[] enCodeFormat = (); SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES"); Cipher cipher = ("AES");// 创建密码器 byte[] byteContent = ("utf-8"); (Cipher.ENCRYPT_MODE, key);// 初始化 byte[] result = (byteContent); return result; // 加密 } catch (NoSuchAlgorithmException e) { (); } catch (NoSuchPaddingException e) { (); } catch (InvalidKeyException e) { (); } catch (UnsupportedEncodingException e) { (); } catch (IllegalBlockSizeException e) { (); } catch (BadPaddingException e) { (); } return null; }

The code has detailed comments, no nonsense

Note: When decrypting, you must pass in the byte array

/**解密 * @param content 待解密内容 * @param password 解密密钥 * @return */ public static byte[] decrypt(byte[] content, String password) { try { KeyGenerator kgen = ("AES"); (128, new SecureRandom(())); SecretKey secretKey = (); byte[] enCodeFormat = (); SecretKeySpec key = new SecretKeySpec(enCodeFormat, "AES"); Cipher cipher = ("AES");// 创建密码器 (Cipher.DECRYPT_MODE, key);// 初始化 byte[] result = (content); return result; // 加密 } catch (NoSuchAlgorithmException e) { (); } catch (NoSuchPaddingException e) { (); } catch (InvalidKeyException e) { (); } catch (IllegalBlockSizeException e) { (); } catch (BadPaddingException e) { (); } return null; }

String content = "test"; String password = "12345678"; //加密 ("加密前：" + content); byte[] encryptResult = encrypt(content, password); //解密 byte[] decryptResult = decrypt(encryptResult,password); ("解密后：" + new String(decryptResult));

The output result is as follows:

Before encryption: test
After decryption: test

But if we modify the test code, as follows:

String content = "test"; String password = "12345678"; //加密 ("加密前：" + content); byte[] encryptResult = encrypt(content, password); try { String encryptResultStr = new String(encryptResult,"utf-8"); //解密 byte[] decryptResult = decrypt(("utf-8"),password); ("解密后：" + new String(decryptResult)); } catch (UnsupportedEncodingException e) { (); }

Then, the system will report the following exception:

: Input length must be multiple of 16 when decrypting with padded cipher
        at .SunJCE_f.b(DashoA13*..)
        at .SunJCE_f.b(DashoA13*..)
        at (DashoA13*..)
        at (DashoA13*..)

This is mainly because the encrypted byte array cannot be cast into a string. In other words, strings and byte arrays are not inverse in this case; to avoid this case, we need to make some revisions, and we can consider converting binary data into hexadecimal representations. There are two main methods:

/**将二进制转换成16进制 * @param buf * @return */ public static String parseByte2HexStr(byte buf[]) { StringBuffer sb = new StringBuffer(); for (int i = 0; i < ; i++) { String hex = (buf[i] & 0xFF); if (() == 1) { hex = '0' + hex; } (()); } return (); }

/**将16进制转换为二进制 * @param hexStr * @return */ public static byte[] parseHexStr2Byte(String hexStr) { if (() < 1) return null; byte[] result = new byte[()/2]; for (int i = 0;i< ()/2; i++) { int high = ((i*2, i*2+1), 16); int low = ((i*2+1, i*2+2), 16); result[i] = (byte) (high * 16 + low); } return result; }

Then, we revise the above test code, as follows:

String content = "test"; String password = "12345678"; //加密 ("加密前：" + content); byte[] encryptResult = encrypt(content, password); String encryptResultStr = parseByte2HexStr(encryptResult); ("加密后：" + encryptResultStr); //解密 byte[] decryptFrom = parseHexStr2Byte(encryptResultStr); byte[] decryptResult = decrypt(decryptFrom,password); ("解密后：" + new String(decryptResult));

The test results are as follows:

Before encryption: test
After encryption: 73C58BAFE578C59366D8C995CD0B9D6D
After decryption: test

 

There is also an encryption method, which you can refer to as follows:

/** * 加密 * * @param content 需要加密的内容 * @param password 加密密码 * @return */ public static byte[] encrypt2(String content, String password) { try { SecretKeySpec key = new SecretKeySpec((), "AES"); Cipher cipher = ("AES/ECB/NoPadding"); byte[] byteContent = ("utf-8"); (Cipher.ENCRYPT_MODE, key);// 初始化 byte[] result = (byteContent); return result; // 加密 } catch (NoSuchAlgorithmException e) { (); } catch (NoSuchPaddingException e) { (); } catch (InvalidKeyException e) { (); } catch (UnsupportedEncodingException e) { (); } catch (IllegalBlockSizeException e) { (); } catch (BadPaddingException e) { (); } return null; }

There are two limitations to this encryption method

• The key must be 16-bit
• The length of the content to be encrypted must be a multiple of 16. If it is not a multiple of 16, the following exception will occur:

: Input length not multiple of 16 bytes
        at .SunJCE_f.a(DashoA13*..)
        at .SunJCE_f.b(DashoA13*..)
        at .SunJCE_f.b(DashoA13*..)
        at (DashoA13*..)
        at (DashoA13*..)

To solve the above exception, you can avoid it by completing the encrypted content.