Here is my security protocol for the use of a service provided by server. It utilises a symmetric key:
- Client requests to use a service
- Server sends back nonce
- Client sends back nonce encrypted with Alice’s key
- Once server verifies key and checks nonce server authorises use of service
Does the use of the nonce prevent the reuse of old authorisations?
What type of symmetric encryption algorithm is best to use in this case?
Are there any serious security flaws?