RSA Key generation with SecKey Xamarin.iOS

Question

I'm trying to generate a public (and private) key pair using the SecKey class from Xamarin.iOS. The KeySize is defined to 1024 bit and this seems to work (if I change this value, the length of the result array is changing too).

I generate the keys with

SecKey.GenerateKeyPair(CreateRsaParams(), out publicKey, out privateKey); 
byte[] key = publicKey.GetExternalRepresentation().ToArray()

(CreateRsaParams() is a function giving back a NSDictionary with the required data)

The problem is: I get a byte array (public key) with 140 Bytes - but depended on the key size it should have only 128 Byte - and I need a 128 Byte public key for data exchange with an other system

(by the way - using PCLCrypto is not an option for me since the project is not allowed to use this 3rd party component)

Does anyone know the problem and know a solution?

Answer 1

Okay, problem solved. If anyone is facing the same problem, you can find the solution at https://forums.developer.apple.com/thread/111109

The problem was not the key, but the wrongly formulated requirement.