A password protocol for establishing secure communications between sensor nodes in a network using secure environmental values (SEV). A first sensor sends a message to a second sensor comprising the first sensor's location and a key encrypted by a first SEV. The second sensor responds with a message comprising a key encrypted by a second SEV and a first nonce encrypted by a session key. The first sensor sends a third message comprising the first nonce and a second nonce encrypted by the session key. The second sensor verifies the first nonce and sends a fourth message comprising the encrypted second nonce. The first sensor then verifies the second nonce.