(* Title: HOL/Auth/Shared
ID: $Id$
Author: Lawrence C Paulson, Cambridge University Computer Laboratory
Copyright 1996 University of Cambridge
Theory of Shared Keys (common to all symmetric-key protocols)
Server keys; initial states of agents; new nonces and keys; function "sees"
*)
Shared = Message + List +
consts
shrK :: agent => key (*symmetric keys*)
rules
isSym_shrK "isSymKey (shrK A)"
consts (*Initial states of agents -- parameter of the construction*)
initState :: [agent set, agent] => msg set
primrec initState agent
(*Server knows all keys; other agents know only their own*)
initState_Server "initState lost Server = Key `` range shrK"
initState_Friend "initState lost (Friend i) = {Key (shrK (Friend i))}"
initState_Spy "initState lost Spy = Key``shrK``lost"
datatype (*Messages, and components of agent stores*)
event = Says agent agent msg
consts
sees1 :: [agent, event] => msg set
primrec sees1 event
(*Spy reads all traffic whether addressed to him or not*)
sees1_Says "sees1 A (Says A' B X) = (if A:{B,Spy} then {X} else {})"
consts
sees :: [agent set, agent, event list] => msg set
primrec sees list
(*Initial knowledge includes all public keys and own private key*)
sees_Nil "sees lost A [] = initState lost A"
sees_Cons "sees lost A (ev#evs) = sees1 A ev Un sees lost A evs"
(*Agents generate "random" nonces. Different traces always yield
different nonces. Same applies for keys.*)
consts
newN :: "event list => nat"
newK :: "event list => key"
rules
inj_shrK "inj shrK"
inj_newN "inj newN"
inj_newK "inj newK"
newK_neq_shrK "newK evs ~= shrK A"
isSym_newK "isSymKey (newK evs)"
end