Error in SignalPreKeyBundle initWithRegistrationId method

[kasas]

Good evening,

we are trying to use Signal with OMEMO in an XMPP app, however we are stuck in this method:

SignalPreKeyBundle* preKey = [[SignalPreKeyBundle alloc] initWithRegistrationId:0 deviceId:deviceId preKeyId:key.preKeyId preKeyPublic:key.publicKey signedPreKeyId:bundle.signedPreKey.preKeyId signedPreKeyPublic:bundle.signedPreKey.publicKey signature:bundle.signedPreKey.signature identityKey:bundle.identityKey error:&error];

As the init method is not able to use prekey publickey generated by the SignalHelper of the same framework. Could you please help us?

As you can see

ec_public_key *pre_key_public = [SignalKeyPair publicKeyFromData:preKeyPublic error:error];
if (!pre_key_public) {
return nil;
}

is returning nil.. the error is domain: "org.whispersystems.SignalProtocol" - code: 4

Thanks in advance