android中的加密傳輸

找到兩種加密算法,一種MD5加密,適用於密碼加密,因為這種算法不可逆;還有一種是RSA加密,這種加密是可逆的:
 
一、MD5加密
 

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" }; 
  
 
        /**
 
         * 轉換字節數組為16進制字串
 
         * 
         * @param b
 
         *            字節數組
 
         * @return 16進制字串
 
         */ 
  
        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; 
  
        } 
  

 
 
二、RSA加密
 

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; 
  
    } 
  

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