1. A method of printing a security document having a security feature, the method including: receiving the security document; receiving identity data, the identity data being at least partially indicative of an identity of the security document, the identity data being encrypted using a public key; determining the identity by decrypting the received identity data using a secret key associated with the public key; generating a signature using the determined identity, the signature being a digital signature of at least part of the identity; generating coded data at least partially indicative of: the identity of the security document; and, at least part of the signature; and, printing the coded data on the security document.