iOS开发之Objective-c的AES加密和解密算法的实现

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 
#import 
#import 

@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+1];
    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 = 0;
    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+1];
    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 = 0;
    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

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

//
//NSString +AES256.h
//

#import 
#import 
#import 

#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 > 0) {

        Byte *datas = (Byte*)[result bytes];
        NSMutableString *output = [NSMutableString stringWithCapacity:result.length * 2];
        for(int i = 0; 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 / 2];
    unsigned char whole_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    int i;
    for (i=0; i < [self length] / 2; i++) {
        byte_chars[0] = [self characterAtIndex:i*2];
        byte_chars[1] = [self characterAtIndex:i*2+1];
        whole_byte = strtol(byte_chars, NULL, 16);
        [data appendBytes:&whole_byte length:1];
    }

    //对数据进行解密
    NSData* result = [data aes256_decrypt:key];
    if (result && result.length > 0) {
        return [[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding]autorelease];
    }
    return nil;
}
@end