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 <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+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 <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 > 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