# Otway Rees
#
# Modelled after the description in the SPORE library
# http://www.lsv.ens-cachan.fr/spore/otwayRees.html
#
#
# Note:
# This protocol uses a ticket so scyther will only be able to verify
# the protocol using the ARACHNE engine (-a)
#


secret const k : Function;
const Fresh: Function;
const Compromised: Function;

usertype String,SessionKey;

protocol otwayRees^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 M: String;
        const Kir: SessionKey;
        var I,R,S: Agent;

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

protocol otwayrees(I,R,S)
{
    role I
    {
        const Ni : Nonce;
        const M : String;
        var Kir : SessionKey;

        send_1(I,R, M,I,R,{Ni,M,I,R}k(I,S) );
        read_4(R,I, M,{Ni,Kir}k(I,S) );

        claim_I1(I, Secret,Kir);
        claim_I2(I, Nisynch);
        claim_I3(I, Empty, (Fresh,Kir));
    }

    role R
    {
        var M : String;
        const Nr : Nonce;
        var Kir : SessionKey;
        var T1,T2: Ticket;

        read_1(I,R, M,I,R, T1 );
        send_2(R,S, M,I,R, T1, { Nr,M,I,R }k(R,S) );
        read_3(S,R, M, T2, { Nr,Kir }k(R,S) );
        send_4(R,I, M, T2 );

        claim_R1(R, Secret,Kir);
        claim_R2(R, Nisynch);
        claim_R3(R, Empty, (Fresh,Kir));
    }

    role S
    {
        var Ni,Nr : Nonce;
        var M : String;
        const Kir : SessionKey;
        
        read_2(R,S, M,I,R, { Ni,M,I,R}k(I,S), { Nr,M,I,R }k(R,S) );
        send_3(S,R, M, { Ni,Kir }k(I,S) , { Nr,Kir }k(R,S) );
    }
}

const Alice, Bob, Eve, Simon: Agent;

untrusted Eve;
compromised k(Eve,Simon);

run otwayrees.A(Alice, Agent, Simon);
run otwayrees.B(Agent, Bob, Simon);
run otwayrees.S(Agent, Agent, Simon);

run otwayrees.A(Agent, Agent, Simon);
run otwayrees.B(Agent, Agent, Simon);
run otwayrees.S(Agent, Agent, Simon);