How to process Oauth nonces on the server side ?

Question

I am writing the provider part of the OAuth protocol on the serverside and I'm cracking my ahead over how much of the nonces sent by OAuth consumers that I need to cache.

According to twitter's docs,

Twitter will only allow a nonce to be used once by your application. Prevents replayed requests.

The question: My implementation will just simply add each nonces received into memcached. But this will take up a lot of memory space. How much of the nonces should I ideally cache and for how long ?

Answer 1

Nonces only need to be unique for all requests using the same timestamp. You should deny requests with a timestamp older then 5 minutes so you only need to store nonces for 5 minutes.

http://tools.ietf.org/html/rfc5849#section-3.3