Session protocol for backward security between paired devices

A device comprising:

• a memory configured to store a first key and a first value corresponding to the first key;
• and
• at least one processor configured to:
• establish a secure communication session with another device based at least in part on the first key, the establishing comprising applying a one-way function to the first key to update the first key to match a second key at the other device when the first value differs from a received second value corresponding to the second key;
• exchange encrypted data with the other device as a part of the secure communication session;
• upon completion of the secure communication session, modify, using the one-way function, the first key;
• and
• store the modified first key in the memory.

A non-transitory machine-readable medium comprising code that, when executed by one or more processors, causes the one or more processors to perform one or more operations, the code comprising:

• code to establish, by a device, a secure communication session with another device based at least in part on a local key, the establishing comprising applying a one-way function to the local key when a local value corresponding to the local key differs from a received remote value corresponding to a remote key;
• code to exchange encrypted data with the other device as a part of the secure communication session;
• code to, upon completion of the secure communication session, modify, using the one-way function, the local key;
• and
• code to store the modified local key.