iOS开发之Objective-c的AES256加密和解密算法的实现

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