Example of AES Encryption

Recently I used to encrypt text content, so I checked the common encryption algorithms:

Des (Data Encryption Standard): symmetric algorithm, Data Encryption Standard, fast, suitable for encrypting a large amount of data;
3DES (Triple DES): It is a symmetric algorithm based on Des. it encrypts a piece of data three times with three different keys, with higher strength;
RC2 and RC4: symmetric algorithms that use variable-length keys to encrypt a large amount of data, faster than DES;
Idea (International Data Encryption Algorithm) International Data Encryption Algorithm, uses a 128-bit key to provide very strong security;
RSA: A Public Key algorithm that supports variable-length keys. The length of the file block to be encrypted is also variable. asymmetric algorithms;
DSA (Digital Signature Algorithm): digital signature algorithm, which is a standard DSS (Digital Signature Standard). It is not an encryption algorithm strictly;
AES (Advanced Encryption Standard): Advanced Encryption Standard, symmetric algorithm, is the next generation of encryption algorithm standard, fast, high security level, currently an implementation of the AES standard is Rijndael algorithm;
Blowfish uses a variable-length key, which can contain up to 448 bits and runs fast;
MD5: it is not an encryption algorithm, but a digest algorithm.

The following example shows how to implement AES encryption and decryption in Java:

Encryption:

/* * encrypt * @param content:  * @param password: */private static byte[] encrypt(String content, String password) {try {KeyGenerator kgen = KeyGenerator.getInstance("AES");kgen.init(128, new SecureRandom(password.getBytes()));SecretKey secretKey = kgen.generateKey();byte[] encodeFormat = secretKey.getEncoded();SecretKeySpec key = new SecretKeySpec(encodeFormat, "AES");Cipher cipher = Cipher.getInstance("AES");byte[] byteContent = content.getBytes("utf-8");cipher.init(Cipher.ENCRYPT_MODE, key);byte[] result = cipher.doFinal(byteContent);return result;} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (NoSuchPaddingException e) {e.printStackTrace();} catch (InvalidKeyException e) {e.printStackTrace();} catch (UnsupportedEncodingException e) {e.printStackTrace();} catch (IllegalBlockSizeException e) {e.printStackTrace();} catch (BadPaddingException e) {e.printStackTrace();}return null;}

Decryption:

/* * decrypt * @param content:  * @param password: */private static byte[] decrypt(byte[] content, String password) {try {KeyGenerator kgen = KeyGenerator.getInstance("AES");kgen.init(128, new SecureRandom(password.getBytes()));SecretKey secretKey = kgen.generateKey();byte[] encodeFormat = secretKey.getEncoded();SecretKeySpec key = new SecretKeySpec(encodeFormat, "AES");Cipher cipher = Cipher.getInstance("AES");cipher.init(Cipher.DECRYPT_MODE, key);byte[] result = cipher.doFinal(content);return result;} catch (NoSuchAlgorithmException e) {e.printStackTrace();} catch (NoSuchPaddingException e) {e.printStackTrace();} catch (InvalidKeyException e) {e.printStackTrace();} catch (IllegalBlockSizeException e) {e.printStackTrace();} catch (BadPaddingException e) {e.printStackTrace();}return null;}

Example:

String content = "test"; string Password = "12345678"; // encrypt the system. out. println ("before encryption:" + content); byte [] encryptresult = encrypt (content, password); // decrypt byte [] decryptresult = decrypt (encryptresult, password); system. out. println ("decrypted:" + new string (decryptresult ));

Output:

Before encryption: test after decryption: Test

If you want to display the data in hexadecimal format after encryption, you can add two functions for binary and hexadecimal conversion.

Convert binary to hexadecimal:

private static String parseByte2HexStr(byte buf[]) {StringBuffer sb = new StringBuffer();for (int i = 0; i < buf.length; i++) {String hex = Integer.toHexString(buf[i] & 0xFF);if (hex.length() == 1) {hex = '0' + hex;}sb.append(hex.toUpperCase());}return sb.toString();}

Hexadecimal conversion to binary:

private static byte[] parseHexStr2Byte(String hexStr) {if (hexStr.length() < 1) {return null;}byte[] result = new byte[hexStr.length() / 2];for (int i = 0; i < hexStr.length() / 2; i++) {int high = Integer.parseInt(hexStr.substring(i*2, i*2+1), 16);int low = Integer.parseInt(hexStr.substring(i*2+1, i*2+2), 16);result[i] = (byte)(high * 16 + low);}return result;}

Example:

String content = "test"; string Password = "12345678"; // encrypt the system. out. println ("before encryption:" + content); byte [] encryptresult = encrypt (content, password); string encryptresultstr = parsebyte2hexstr (encryptresult); system. out. println ("encrypted:" + encryptresultstr); // decrypt byte [] decryptfrom = parsehexstr2byte (encryptresultstr); byte [] decryptresult = decrypt (decryptfrom, password); system. out. println ("decrypted:" + new string (decryptresult ));

Output:

Before encryption: test after encryption: 73c58bafe578c591_d8c995cd0b9d6d after decryption: Test

Note: the code can be found in networks.