# Lowe modified Denning-Sacco shared key
#
# Modelled after the description in the SPORE library
# http://www.lsv.ens-cachan.fr/spore/denningSaccoLowe.html
#
# Note:
# This protocol uses a ticket so scyther will only be able to verify
# the protocol using the ARACHNE engine (-a)
#
# Note:
# According to SPORE there are no attacks on this protocol, scyther
# finds one however. This has to be investigated further.

usertype Key;
usertype SessionKey;
usertype TimeStamp;
secret k: Function;
usertype PseudoFunction;
const dec: PseudoFunction;

protocol denningSaccoLowe(I,R,S)
{
    role I
    {
        var W: Ticket;
        var Kir: SessionKey;
        var T: TimeStamp;
        var Nr: Nonce;

        send_1(I,S, I,R );
        read_2(S,I, {R, Kir, T, W}k(I,S) );
        send_3(I,R, W);
        read_4(R,I, {Nr}Kir);
        send_5(I,R, {{Nr}dec}Kir);
        claim_6(I,Niagree);
    }    
    
    role R
    {
        var Kir: SessionKey;
        var T: TimeStamp;
        const Nr: Nonce;

        read_3(I,R, {Kir,I,T}k(R,S));
        send_4(R,I, {Nr}Kir);
        read_5(I,R, {{Nr}dec}Kir);
        claim_8(R,Niagree);
    }
    
    role S
    {
        var W: Ticket;
        const Kir: SessionKey;
        const T: TimeStamp;

        read_1(I,S, I,R );
        send_2(S,I, {R, Kir, T, {Kir, I,T}k(R,S)}k(I,S));
    }    
}

const Alice,Bob,Simon,Eve: Agent;

untrusted Eve;
const kee: SessionKey;
const tee: TimeStamp;
compromised k(Eve,Simon);



# General scenario, 2 parallel runs of the protocol
# Note because the modelchecker does not support tickets this might not
# be very useful

run denningSaccoLowe.I(Agent,Agent,Simon);
run denningSaccoLowe.R(Agent,Agent,Simon);
run denningSaccoLowe.S(Agent,Agent,Simon);
run denningSaccoLowe.I(Agent,Agent,Simon);
run denningSaccoLowe.R(Agent,Agent,Simon);
run denningSaccoLowe.S(Agent,Agent,Simon);