3DES Encryption / Decryption using ECB in iOS

Question

i'm making an application , in which i have to encrypt a string using 3DES encryption in ECB mode. im using "mykey" as a key.

+ (NSData *)tripleDesEncryptData:(NSData *)inputData
                             key:(NSData *)keyData
                           error:(NSError **)error
{
NSParameterAssert(inputData);
NSParameterAssert(keyData);

size_t outLength;

NSAssert(keyData.length == kCCKeySize3DES, @"the keyData is an invalid size");

NSMutableData *outputData = [NSMutableData dataWithLength:(inputData.length  +  kCCBlockSize3DES)];

CCCryptorStatus
    result = CCCrypt(kCCEncrypt, // operation
                     kCCAlgorithm3DES, // Algorithm
                     0, // options
                     keyData.bytes, // key
                     keyData.length, // keylength
                     nil,// iv
                     inputData.bytes, // dataIn
                     inputData.length, // dataInLength,
                     outputData.mutableBytes, // dataOut
                     outputData.length, // dataOutAvailable
                     &outLength); // dataOutMoved

    if (result != kCCSuccess) {
        if (error != NULL) {
            *error = [NSError errorWithDomain:@"com.your_domain.your_project_name.your_class_name."
                                         code:result
                                     userInfo:nil];
        }
        return nil;
    }
    [outputData setLength:outLength];
    NSLog(@"here is my output %@",outputData);
    return outputData;
}

i am getting an exception because of invalid Key size. (i'm using this 'mykey' as my key). I'm not expert in encryption. Any kind of Help will be highly appreciated.

Answer 1

You're getting "invalid key size" because, well, your key is an invalid size. I'm not sure what else you were expecting the system to tell you. The 3DES algorithm expects a key size of 24 bytes and "mykey" is too short.

Even apart from the length issue, in general it is a bad idea to directly use strings as cryptographic keys. Instead you should use an accepted password-to-key algorithm such as PBKDF2.