# Lowe modified Wide Mouthed Frog
#
# Modelled after the description in the SPORE library
# http://www.lsv.ens-cachan.fr/spore/wideMouthedFrogLowe.html
#
# Note:
# According to SPORE there are no known attacks on this protocol, scyther
# finds one however this has to do with the unusual assumption that every 
# agent can recognise and will reject to read messages that it has created
# itself.

usertype SessionKey;
usertype TimeStamp;
usertype ExpiredTimeStamp;
const succ,pred: Function;
inversekeys (succ,pred);
const Fresh: Function;
const Compromised: Function;

protocol wmf-Lowe(I,R,S)
{
    role I
    {
        fresh Kir: SessionKey;
        fresh Ti: TimeStamp;
        var Kr: SessionKey;
        var Nr: Nonce;

        send_1(I,S, I, {Ti, R, Kir}k(I,S)); 
        read_3(R,I,{Nr}Kir);
        send_4(I,R,{{Nr}succ}Kir);

        claim_I1(I,Secret,Kir);
        claim_I2(I,Nisynch);
        claim_I3(I,Empty,(Fresh,Kir));
    }    
    
    role R
    {
        var Ts: TimeStamp;
        var Kir: SessionKey;
        fresh Nr: Nonce;

        read_2(S,R, {Ts, I, Kir}k(R,S) );
        send_3(R,I, {Nr}Kir);
        read_4(I,R, {{Nr}succ}Kir);

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

    role S
    {
        var Kir: SessionKey;
        fresh Ts: TimeStamp;
        var Ti: TimeStamp;

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