I am working with a networked embedded device with AES-128 and no public key cryptography (1KB RAM, 8KB flash). At install, the device is pre-loaded with a longterm AES-128 key known also to the server.
What patent free protocols exist for securely distributing an authenticated session key using the existing symmetric key? (with no trusted third party)
Janson-Tsudik 2PKDP looks ideal, but appears to be patented.