最近在考虑数据加密方面的需求，所以对数据加密简单的看了一下，当然不是看的原理，只是看看怎么能够实现。现在我们需要实现的是移动端和后台（java）数据加解密的配合，开始的时候考虑的使用RSA，因为RSA是非对称加密，更加安全点，但是RSA加密的过程中，ios公钥加密的数据，后台java是能够解密成功，但是后台java私钥加密的东西，前端ios，就没有解密成功，实验了很多方法，最终也没有成功，所以就放弃了，转向了安全性差一点的DES加密。

对于DES、RSA的介绍，自己百度去吧，因为我也说不明白。（上面我没有提Android，因为Android使用的是java，所以应该跟后台一致）

下面废话不多说，直接贴上代码：

IOS，需要引入GTMBase64.h、GTMBase64.m、GTMDefines.h，这个github上面有我，自己搜搜吧，还有<CommonCrypto/CommonCryptor.h>。

[objc] view plaincopy
#import "ViewController.h"
#import <CommonCrypto/CommonCryptor.h>
#import "GTMBase64.h"  @interface ViewController ()  @end  @implementation ViewController  -(void)viewDidLoad {  [super viewDidLoad];  NSString *key = @"这是个key";  NSString *encryptedData = [self encryptUseDES:@"this is a text" key:key];  NSLog(@"加密后的数据是:%@", encryptedData);  NSLog(@"解密后的数据是:%@", [self decryptUseDES:encryptedData key:key]);
}  -(void)didReceiveMemoryWarning {  [super didReceiveMemoryWarning];  // Dispose of any resources that can be recreated.
}  /*字符串加密 *参数 *plainText : 加密明文 *key        : 密钥 64位 */
-(NSString *) encryptUseDES:(NSString *)plainText key:(NSString *)key
{  NSString *ciphertext = nil;  const charchar *textBytes = [plainText UTF8String];  NSUInteger dataLength = [plainText length];  unsigned char buffer[1024];  memset(buffer, 0, sizeof(char));  Byte iv[] = {1,2,3,4,5,6,7,8};  size_t numBytesEncrypted = 0;  CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmDES,  kCCOptionPKCS7Padding,  [key UTF8String], kCCKeySizeDES,  iv,  textBytes, dataLength,  buffer, 1024,  &numBytesEncrypted);  if (cryptStatus == kCCSuccess) {  NSData *data = [NSData dataWithBytes:buffer length:(NSUInteger)numBytesEncrypted];  ciphertext = [[NSString alloc] initWithData:[GTMBase64 encodeData:data] encoding:NSUTF8StringEncoding];  }  return ciphertext;
}  //解密
-(NSString *) decryptUseDES:(NSString*)cipherText key:(NSString*)key
{  NSData* cipherData = [GTMBase64 decodeString:cipherText];  unsigned char buffer[1024];  memset(buffer, 0, sizeof(char));  size_t numBytesDecrypted = 0;  Byte iv[] = {1,2,3,4,5,6,7,8};  CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,  kCCAlgorithmDES,  kCCOptionPKCS7Padding,  [key UTF8String],  kCCKeySizeDES,  iv,  [cipherData bytes],  [cipherData length],  buffer,  1024,  &numBytesDecrypted);  NSString* plainText = nil;  if (cryptStatus == kCCSuccess) {  NSData* data = [NSData dataWithBytes:buffer length:(NSUInteger)numBytesDecrypted];  plainText = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];  }  return plainText;
}  @end 

java 代码：需要自己引入sun.misc.BASE64Decoder.jar

[java] view plaincopy
package com.yue;  import java.io.IOException;
import java.security.SecureRandom;  import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;  import Decoder.BASE64Decoder;
import Decoder.BASE64Encoder;  public class DesUtil {  private final static String DES = "DES";  public static void main(String[] args) throws Exception {  String data = "123 456";  String key = "abcdefgh";  System.err.println(encrypt(data, key));  System.err.println(decrypt(encrypt(data, key), key));  System.out.println(decrypt("JF5dX/TlOg529KAhh+vywjzIp5Msktmf", key));  }  /** * Description 根据键值进行加密 * @param data  * @param key  加密键byte数组 * @return * @throws Exception */  public static String encrypt(String data, String key) throws Exception {  byte[] bt = encrypt(data.getBytes(), key.getBytes());  String strs = new BASE64Encoder().encode(bt);  return strs;  }  /** * Description 根据键值进行解密 * @param data * @param key  加密键byte数组 * @return * @throws IOException * @throws Exception */  public static String decrypt(String data, String key) throws IOException,  Exception {  if (data == null)  return null;  BASE64Decoder decoder = new BASE64Decoder();  byte[] buf = decoder.decodeBuffer(data);  byte[] bt = decrypt(buf,key.getBytes());  return new String(bt);  }  /** * Description 根据键值进行加密 * @param data * @param key  加密键byte数组 * @return * @throws Exception */  private static byte[] encrypt(byte[] data, byte[] key) throws Exception {  // 生成一个可信任的随机数源  SecureRandom sr = new SecureRandom();  // 从原始密钥数据创建DESKeySpec对象  DESKeySpec dks = new DESKeySpec(key);  // 创建一个密钥工厂，然后用它把DESKeySpec转换成SecretKey对象  SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);  SecretKey securekey = keyFactory.generateSecret(dks);  // Cipher对象实际完成加密操作  Cipher cipher = Cipher.getInstance(DES);  // 用密钥初始化Cipher对象  cipher.init(Cipher.ENCRYPT_MODE, securekey, sr);  return cipher.doFinal(data);  }  /** * Description 根据键值进行解密 * @param data * @param key  加密键byte数组 * @return * @throws Exception */  private static byte[] decrypt(byte[] data, byte[] key) throws Exception {  // 生成一个可信任的随机数源  SecureRandom sr = new SecureRandom();  // 从原始密钥数据创建DESKeySpec对象  DESKeySpec dks = new DESKeySpec(key);  // 创建一个密钥工厂，然后用它把DESKeySpec转换成SecretKey对象  SecretKeyFactory keyFactory = SecretKeyFactory.getInstance(DES);  SecretKey securekey = keyFactory.generateSecret(dks);  // Cipher对象实际完成解密操作  Cipher cipher = Cipher.getInstance(DES);  // 用密钥初始化Cipher对象  cipher.init(Cipher.DECRYPT_MODE, securekey, sr);  return cipher.doFinal(data);  }
}  

代码下载地址：http://download.csdn.net/detail/mengxiangyue/8028311