RSA Key and signature lengths using gcry_pk_genkey/sign

[James Hume]

Hello,

Hope i'm posting this to the right mailing list, apologies if not. I
am using the gcry_pk_* functions to generate keys and signatures. I
have seen that sometimes the key lengths can vary, as can the
signature length which either seems to be 128 bytes or 129 bytes (in
which case there always seems to be a  leading null byte). Should the
library be returning varying signature/key sizes?

Thanks for any help in advance.

--
James