iPhone开发技巧之数据篇（2）— iPhone程序中的加密处理

CCCrypt
在Objective-C语言中，加密时常用到CCCrypt(3cc) Mac OS X Manual Pagehttp://developer.apple.com/library/mac/#DOCUMENTATION/Darwin/Reference/ManPages/man3/CCCrypt.3cc.html 。下面的代码使用 CCCrypt() ，给 NSData 类增加了 AES256EncryptWithKey, AES256DecryptWithKey 方法。
1. #import <CommonCrypto/CommonCryptor.h>
2. 
3. @implementation NSData (Additions)
4. 
5. @class NSString;
6. 
7. - (NSData *)AES256EncryptWithKey:(NSString *)key {
8.         char keyPtr[kCCKeySizeAES256+1];
9.         bzero(keyPtr, sizeof(keyPtr));
10. 
11.         [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];
12. 
13.         NSUInteger dataLength = [self length];
14. 
15.         size_t bufferSize = dataLength + kCCBlockSizeAES128;
16.         void *buffer = malloc(bufferSize);
17. 
18.         size_t numBytesEncrypted = 0;
19.         CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,
20.                                                                          kCCOptionPKCS7Padding | kCCOptionECBMode,
21.                                                                          keyPtr, kCCBlockSizeAES128,
22.                                                                          NULL,
23.                                                                          [self bytes], dataLength,
24.                                                                          buffer, bufferSize,
25.                                          &nbs