由于最近在做蓝牙项目，和固件程序通讯需要使用到AES加解密，特此记录下具体过程。
加密方法如下：

+(NSString *)AES128Encrypt:(NSString *)plainText key:(NSString *)key{
    NSData *keyData = [self dataForHexString:key];
    Byte *aKey = (Byte *)[keyData bytes];
    
    NSData *data = [plainText dataUsingEncoding:NSUTF8StringEncoding];
    char dataPtr[kCCKeySizeAES128];
    memcpy(dataPtr, [data bytes], [data length]);
    for(int i = 0; i < 8; i++){
        dataPtr[i + 8] = 0x00;
    }
    data = [NSData dataWithBytes:dataPtr length:kCCKeySizeAES128];
    
    unsigned char result[kCCKeySizeAES128];
    bzero(result, kCCKeySizeAES128);
    size_t numBytesCrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCEncrypt,
                                          kCCAlgorithmAES128,
                                          kCCOptionECBMode,
                                          aKey,
                                          kCCKeySizeAES128,
                                          NULL,
                                          data.bytes,
                                          16,
                                          result,
                                          sizeof(result),
                                          &numBytesCrypted);
    if(cryptStatus == kCCSuccess){
        NSData *ret = [NSData dataWithBytes:result length:numBytesCrypted];
        return [self hexStringFromData:ret];
    }
    return nil;
}

解密方法如下：

+(NSString *)AES128Decrypt:(NSString *)encryptText key:(NSString *)key{
    NSData *keyData = [self dataForHexString:key];
    Byte *aKey = (Byte *)[keyData bytes];
    
    NSData *data = [self dataForHexString:encryptText];
    data = [NSData dataWithBytes:dataPtr length:kCCKeySizeAES128];
    */
    
    unsigned char result[kCCKeySizeAES128];
    bzero(result, sizeof(result));
    size_t numBytesCrypted = 0;
    CCCryptorStatus cryptStatus = CCCrypt(kCCDecrypt,
                                          kCCAlgorithmAES128,
                                          kCCOptionECBMode,
                                          aKey,
                                          kCCKeySizeAES128,
                                          NULL,
                                          data.bytes,
                                          16,
                                          result,
                                          sizeof(result),
                                          &numBytesCrypted);
    if(cryptStatus == kCCSuccess){
        NSData *ret = [NSData dataWithBytes:result length:numBytesCrypted];
        NSString *string = [self hexStringFromData:ret];
        return [self stringFromHexString:string];
    }
    return nil;
}

相关方法如下：

+ (NSData*)dataForHexString:(NSString*)hexString{
    if (hexString == nil) {
        return nil;
    }
    const char* ch = [[hexString lowercaseString] cStringUsingEncoding:NSUTF8StringEncoding];
    NSMutableData* data = [NSMutableData data];
    while (*ch) {
        if (*ch == ' ') {
            continue;
        }
        char byte = 0;
        if ('0' <= *ch && *ch <= '9') {
            byte = *ch - '0';
        }else if ('a' <= *ch && *ch <= 'f') {
            byte = *ch - 'a' + 10;
        }else if ('A' <= *ch && *ch <= 'F') {
            byte = *ch - 'A' + 10;
        }
        ch++;
        byte = byte << 4;
        if (*ch) {
            if ('0' <= *ch && *ch <= '9') {
                byte += *ch - '0';
            } else if ('a' <= *ch && *ch <= 'f') {
                byte += *ch - 'a' + 10;
            }else if('A' <= *ch && *ch <= 'F'){
                byte += *ch - 'A' + 10;
            }
            ch++;
        }
        [data appendBytes:&byte length:1];
    }
    return data;
}

// 普通字符串转换为十六进制
+ (NSString *)hexStringFromData:(NSData *)data {
    Byte *bytes = (Byte *)[data bytes];
    // 下面是Byte 转换为16进制。
    NSString *hexStr = @"";
    for(int i=0; i<[data length]; i++) {
        NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i] & 0xff]; //16进制数
        newHexStr = [newHexStr uppercaseString];
        
        if([newHexStr length] == 1) {
            newHexStr = [NSString stringWithFormat:@"0%@",newHexStr];
        }
        
        hexStr = [hexStr stringByAppendingString:newHexStr];
        
    }
    return hexStr;
}