1. MD5加密，常用于加密用户名密码，当用户验证时。

protected byte[] encrypt(byte[] obj){ try { MessageDigest md5 = MessageDigest.getInstance("MD5"); md5.update(obj); return md5.digest(); } catch (NoSuchAlgorithmException e){ e.printStackTrace(); } }

　　2. SHA加密，与MD5相似的用法，只是两者的算法不同。

protected byte[] encrypt(byte[] obj) { try { MessageDigest sha = MessageDigest.getInstance("SHA"); sha.update(obj); return sha.digest(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } }

　　3. RSA加密，RAS加密允许解密。常用于文本内容的加密。

import java.security.KeyPair;  import java.security.KeyPairGenerator;  import java.security.interfaces.RSAPrivateKey;  import java.security.interfaces.RSAPublicKey;  import javax.crypto.Cipher;　　/** *//** * RSAEncrypt *  * @author maqujun * @see */ public class RSAEncrypt { /** *//** * Main method for RSAEncrypt. * @param args */ public static void main(String[] args) { try ...{ RSAEncrypt encrypt = new RSAEncrypt(); 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; } }