原文：http://www.lidaren.com/archives/1470

高级加密标准（Advanced Encryption Standard，AES），又称Rijndael加密法。 以下实现代码中分别为NSData和NSString增加了一个Category。使用时直接调用即可。

需要注意的是，AES并不能作为HASH算法，加密并解密后的结果，并不一定与原文相同，使用时请注意进行结果验算。例如解密原文的长度，格式规则等。 NG实例

原文：170987350

密码：170

Objective-c的AES加密和解密算法的具体实现代码如下： 1.拓展NSData，增加AES256加密方法

 //

 //NSData+AES256.h

 //

 #import <Foundation/Foundation.h>

 #import <CommonCrypto/CommonDigest.h>

 #import <CommonCrypto/CommonCryptor.h>

 @interface NSData(AES256)

 -(NSData *) aes256_encrypt:(NSString *)key;

 -(NSData *) aes256_decrypt:(NSString *)key;

 @end

 //

 //NSData+AES256.m

 //

 #import "NSData+AES256.h"

 @implementation NSData(AES256)

 - (NSData *)aes256_encrypt:(NSString *)key   //加密

 {

   char keyPtr[kCCKeySizeAES256+];

   bzero(keyPtr, sizeof(keyPtr));

   [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

   NSUInteger dataLength = [self length];

   size_t bufferSize = dataLength + kCCBlockSizeAES128;

   void *buffer = malloc(bufferSize);

   size_t numBytesEncrypted = ;

   CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt, kCCAlgorithmAES128,

                       kCCOptionPKCS7Padding | kCCOptionECBMode,

                       keyPtr, kCCBlockSizeAES128,

                       NULL,

                       [self bytes], dataLength,

                       buffer, bufferSize,

                       &numBytesEncrypted);

   if (cryptStatus == kCCSuccess) {

     return [NSData dataWithBytesNoCopy:buffer length:numBytesEncrypted];

   }

   free(buffer);

   return nil;

 }

 - (NSData *)aes256_decrypt:(NSString *)key   //解密

 {

   char keyPtr[kCCKeySizeAES256+];

   bzero(keyPtr, sizeof(keyPtr));

   [key getCString:keyPtr maxLength:sizeof(keyPtr) encoding:NSUTF8StringEncoding];

   NSUInteger dataLength = [self length];

   size_t bufferSize = dataLength + kCCBlockSizeAES128;

   void *buffer = malloc(bufferSize);

   size_t numBytesDecrypted = ;

   CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt, kCCAlgorithmAES128,

                       kCCOptionPKCS7Padding | kCCOptionECBMode,

                       keyPtr, kCCBlockSizeAES128,

                       NULL,

                       [self bytes], dataLength,

                       buffer, bufferSize,

                       &numBytesDecrypted);

   if (cryptStatus == kCCSuccess) {

     return [NSData dataWithBytesNoCopy:buffer length:numBytesDecrypted];

   }

   free(buffer);

   return nil;

 }

 @end

 .拓展NSString，增加AES256加密方法，需要导入NSData+AES256.h

 //

 //NSString +AES256.h

 //

 #import <Foundation/Foundation.h>

 #import <CommonCrypto/CommonDigest.h>

 #import <CommonCrypto/CommonCryptor.h>

 #import "NSData+AES256.h"

 @interface NSString(AES256)

 -(NSString *) aes256_encrypt:(NSString *)key;

 -(NSString *) aes256_decrypt:(NSString *)key;

 @end

 //

 //NSString +AES256.h

 //

 @implementation NSString(AES256)

 -(NSString *) aes256_encrypt:(NSString *)key

 {

   const char *cstr = [self cStringUsingEncoding:NSUTF8StringEncoding];

   NSData *data = [NSData dataWithBytes:cstr length:self.length];

   //对数据进行加密

   NSData *result = [data aes256_encrypt:key];

   //转换为2进制字符串

   if (result && result.length > ) {

     Byte *datas = (Byte*)[result bytes];

     NSMutableString *output = [NSMutableString stringWithCapacity:result.length * ];

     for(int i = ; i < result.length; i++){

       [output appendFormat:@"%02x", datas[i]];

     }

     return output;

   }

   return nil;

 }

 -(NSString *) aes256_decrypt:(NSString *)key

 {

   //转换为2进制Data

   NSMutableData *data = [NSMutableData dataWithCapacity:self.length / ];

   unsigned char whole_byte;

   char byte_chars[] = {'\0','\0','\0'};

   int i;

   for (i=; i < [self length] / ; i++) {

     byte_chars[] = [self characterAtIndex:i*];

     byte_chars[] = [self characterAtIndex:i*+];

     whole_byte = strtol(byte_chars, NULL, );

     [data appendBytes:&whole_byte length:];

   }

   //对数据进行解密

   NSData* result = [data aes256_decrypt:key];

   if (result && result.length > ) {

     return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding];

   }

   return nil;

 }

 @end