Java encryption technology (II) -- symmetric encryption algorithm des & AES

From: http://snowolf.iteye.com/blog/380034

Next, we will introduce symmetric encryption algorithms. The most common is des data encryption algorithms.
Des
Des-Data Encryption Standard, which is the data encryption algorithm. It was published by IBM in 1975. The DES algorithm has three entry parameters: Key, data, and mode. Among them, the key is 8 bytes in 64-bit, which is the key of the DES algorithm; data is also 8 bytes in 64-bit, which is the data to be encrypted or decrypted; the mode is des, which can be encrypted or decrypted.
The DES algorithm converts a 64-bit plaintext input block to a 64-bit ciphertext output block. The key used by the DES algorithm is also 64-bit.

The Java code is as follows:For the coder class, see
Java encryption technology (I)

Java code
 

Import Java. security. key; import Java. security. securerandom; import javax. crypto. cipher; import javax. crypto. keygenerator; import javax. crypto. secretkey; import javax. crypto. secretkeyfactory; import javax. crypto. spec. deskeyspec;/*** des security coding component ** <PRE> * supports des, desede (tripledes, 3DES), AES, blowfish, RC2, and RC4 (arcfour) * des key size must be equal to 56 * desede (tripledes) key size must be equal to 112 or 1 68 * AES key size must be equal to 128,192 or 256, but 192 and 256 bits may not be available * blowfish key size must be multiple of 8, and can only range from 32 to 448 (random SIVE) * RC2 key size must be between 40 and 1024 bits * RC4 (arcfour) key size must be between 40 and 1024 bits * pay attention to JDK document http ://... /docs/technotes/guides/security/sunproviders.html * </PRE> ** @ author liangdong * @ v Ersion 1.0 * @ since 1.0 */public abstract class descoder extends coder {/*** algorithm <br> * can be replaced by any of the following algorithms, at the same time, the size of the key value changes accordingly. ** <PRE> * des key size must be equal to 56 * desede (tripledes) key size must be equal to 112 or 168 * AES key size must be equal to 128,192 or 256, but 192 and 256 bits may not be available * blowfish key size must be multiple of 8, and can only range from 32 to 448 (random SIVE) * RC2 key size must be between 40 and 1024 bits * RC4 (arcfour) key size must be between 40 and 1024 bits * </PRE> ** in Use the following code in the key Tokey (byte [] Key) Method * <code> secretkey = new secretkeyspec (Key, algorithm ); </code> replace * <code> * deskeyspec DKS = new deskeyspec (key); * secretkeyfactory keyfactory = secretkeyfactory. getinstance (algorithm); * secretkey = keyfactory. generatesecret (DKS); * </code> */public static final string algorithm = "des "; /*** convert the key <br> ** @ Param key * @ return * @ throws exception */Private Static key Tokey (byte [] Key) throws exception {deskeyspec DKS = new deskeyspec (key); secretkeyfactory keyfactory = secretkeyfactory. getinstance (algorithm); secretkey = keyfactory. generatesecret (DKS); // when using other symmetric encryption algorithms, such as AES and blowfish, replace the preceding three lines of code with the following code: // secretkey = new secretkeyspec (key, algorithm); Return secretkey;}/*** decrypt ** @ Param data * @ Param key * @ return * @ throws Exception */public static byte [] decrypt (byte [] data, string key) throws exception {key K = Tokey (decryptbase64 (key); cipher = cipher. getinstance (algorithm); cipher. init (cipher. decrypt_mode, k); Return cipher. dofinal (data );} /*** encrypt ** @ Param data * @ Param key * @ return * @ throws exception */public static byte [] encrypt (byte [] data, string key) throws exception {key K = Tokey (decryptbase64 (K ); Cipher = cipher. getinstance (algorithm); cipher. init (cipher. encrypt_mode, k); Return cipher. dofinal (data);}/*** generate key ** @ return * @ throws exception */public static string initkey () throws exception {return initkey (null );} /*** generate the key ** @ Param seed * @ return * @ throws exception */public static string initkey (string seed) throws exception {securerandom = NULL; If (seed! = NULL) {securerandom = new securerandom (decryptbase64 (SEED);} else {securerandom = new securerandom ();} keygenerator kg = keygenerator. getinstance (algorithm); kg. init (securerandom); secretkey = kg. generatekey (); Return encryptbase64 (secretkey. getencoded ());}}

Continuing with the implementation of the previous class, we use MD5 and Sha to encrypt the string to generate a key. This is a common key generation method.
A test class: Java code
 

Import static Org. JUnit. assert. *; import Org. JUnit. test;/***** @ author liangdong * @ version 1.0 * @ since 1.0 */public class descodertest {@ testpublic void test () throws exception {string inputstr = "des "; string key = descoder. initkey (); system. err. println ("Original: \ t" + inputstr); system. err. println ("key: \ t" + key); byte [] inputdata = inputstr. getbytes (); inputdata = descoder. encrypt (inputdata, key); system. err. println ("encrypted: \ t" + descoder. encryptbase64 (inputdata); byte [] outputdata = descoder. decrypt (inputdata, key); string outputstr = new string (outputdata); system. err. println ("decrypted: \ t" + outputstr); assertequals (inputstr, outputstr );}}

The output is as follows: Console code
 

Original article: des key: f3wetrrv6q0 = encrypted: c6qe9onizry = decrypted: des

The output from the console is consistent with the encryption and decryption results. This is a simple encryption and decryption method with only one key.
In fact, Des has many siblings, such as desede (tripledes), AES, blowfish, RC2, and RC4 (arcfour ). Here I will not elaborate much about it. The same is true. You only need to replace algorithm with the corresponding value and make a code replacement.Secretkey = new secretkeyspec (Key, algorithm );The key length is different.

Java code
 

/*** Des key size must be equal to 56 * desede (tripledes) key size must be equal to 112 or 168 * AES key size must be equal to 128,192 or 256, but 192 and 256 bits may not be available * blowfish key size must be multiple of 8, and can only range from 32 to 448 (random SIVE) * RC2 key size must be between 40 and 1024 bits * RC4 (arcfour) key size must be between 40 and 1024 bits **/