# 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;
usertype ExpiredTimeStamp;
secret k: Function;
usertype PseudoFunction;
const dec: PseudoFunction;
const Fresh: Function;
const Compromised: Function;

protocol denningSacco-Lowe^KeyCompromise(C)
{
    // Read the names of 3 agents and disclose a session between them including
    // corresponding session key to simulate key compromise
    role C {
        const Ni,Nr: Nonce;
        const Kir: SessionKey;
        const T: ExpiredTimeStamp;
        var I,R,S: Agent;

        read_C1(C,C,    I,R,S);
        send_C2(C,C,    (I,R),
                        {R,Kir,T,{Kir,I,T}k(R,S)}k(I,S),
                        {Kir,I,T}k(R,S),
                        {Nr}Kir,
                        {{Nr}dec}Kir,
                        Kir
               );
        claim_C3(C,Empty, (Compromised,Kir));
    }
}

protocol denningSacco-Lowe(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_I1(I,Niagree);
        claim_I2(I,Nisynch);
        claim_I3(I,Secret,Kir);
        claim_I4(I,Empty,(Fresh,Kir));
    }    
    
    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_R1(R,Niagree);
        claim_R2(R,Nisynch);
        claim_R3(R,Secret,Kir);
        claim_R4(R,Empty,(Fresh,Kir));
    }
    
    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 denningSacco-Lowe.I(Agent,Agent,Simon);
run denningSacco-Lowe.R(Agent,Agent,Simon);
run denningSacco-Lowe.S(Agent,Agent,Simon);
run denningSacco-Lowe.I(Agent,Agent,Simon);
run denningSacco-Lowe.R(Agent,Agent,Simon);
run denningSacco-Lowe.S(Agent,Agent,Simon);