Encrypted transmission in Android

Find two encryption algorithms, one MD5 encryption, which is applicable to password encryption, because this algorithm is irreversible; the other is RSA encryption, Which is reversible:

1. MD5 Encryption

 

 

Import Java. security. messagedigest; public class MD5 {private final static string [] hexdigits = {"0", "1", "2", "3", "4", "5 ", "6", "7", "8", "9", "A", "B", "C", "D", "E ", "F "}; /*** convert the byte array to a hexadecimal string ** @ Param B * byte array * @ return hexadecimal string */public static string bytearraytohexstring (byte [] B) {stringbuffer resultsb = new stringbuffer (); For (INT I = 0; I <B. length; I ++) {resultsb. append (bytetohexstring (B [I]);} return resultsb. tostring ();} Private Static string bytetohexstring (byte B) {int n = B; If (n <0) n = 256 + N; int d1 = N/16; int D2 = n % 16; return hexdigits [D1] + hexdigits [D2];} public static string md5encode (string origin) {string resultstring = NULL; try {resultstring = new string (origin); messagedigest MD = messagedigest. getinstance ("MD5"); resultstring = bytearraytohexstring (MD. digest (resultstring. getbytes ();} catch (exception ex) {} return resultstring ;}}

 

Ii. RSA Encryption

 

import java.security.KeyPair; import java.security.KeyPairGenerator; import java.security.interfaces.RSAPrivateKey; import java.security.interfaces.RSAPublicKey; import javax.crypto.Cipher; /** * RSAEncrypt * * @author chen * @see */ public class Rsaencrype {    /**      * Main method for RSAEncrypt.      * @param args      */     public static void main(String[] args) {         try {             Rsaencrype encrypt = new Rsaencrype();                          String encryptText = "encryptText";             KeyPairGenerator keyPairGen = KeyPairGenerator.getInstance("RSA");             keyPairGen.initialize(1024);             KeyPair keyPair = keyPairGen.generateKeyPair();             // Generate keys             RSAPrivateKey privateKey = (RSAPrivateKey) keyPair.getPrivate();             RSAPublicKey publicKey = (RSAPublicKey) keyPair.getPublic();                          byte[] e = encrypt.encrypt(publicKey, encryptText.getBytes());             byte[] de = encrypt.decrypt(privateKey,e);             System.out.println(encrypt.bytesToString(e));             System.out.println(encrypt.bytesToString(de));         } catch (Exception e) {             e.printStackTrace();         }     }         /**      * Change byte array to String.      * @return byte[]      */     protected String bytesToString(byte[] encrytpByte) {         String result = "";         for (Byte bytes : encrytpByte) {             result += (char) bytes.intValue();         }         return result;     }         /**      * Encrypt String.      * @return byte[]      */     protected byte[] encrypt(RSAPublicKey publicKey, byte[] obj)  {         if (publicKey != null) {             try {                 Cipher cipher = Cipher.getInstance("RSA");                 cipher.init(Cipher.ENCRYPT_MODE, publicKey);                 return cipher.doFinal(obj);             } catch (Exception e) {                 e.printStackTrace();             }         }         return null;     }     /**      * Basic decrypt method      * @return byte[]      */     protected byte[] decrypt(RSAPrivateKey privateKey, byte[] obj) {         if (privateKey != null) {                 try {                     Cipher cipher = Cipher.getInstance("RSA");                     cipher.init(Cipher.DECRYPT_MODE, privateKey);                     return cipher.doFinal(obj);                 } catch (Exception e) {                     e.printStackTrace();                 }             }             return null;     } }