# BAN modified Andrew Secure RPC
#
# Modelled after the description in the SPORE library
# http://www.lsv.ens-cachan.fr/spore/andrewBAN.html
#
# Note:
# The shared key between I and R is modelled as k(I,R) currently
# there is no way to express that this key is equal to k(R,I)
# So it is possile that certain attacks that use this property are not found
# 
# Note:
# According to SPORE there are no known attacks on this protocol
#
usertype SessionKey;
const Fresh: Function;
const Compromised: Function;

protocol andrew-Ban(I,R)
{
    role I
    {
        fresh ni: Nonce;
        var nr,nr2: Nonce;
        var kir: SessionKey;

        send_1(I,R, I,{ni}k(I,R) );
        recv_2(R,I, {ni,nr}k(I,R) );
        send_3(I,R, {nr}k(I,R) );
        recv_4(R,I, {kir,nr2,ni}k(I,R) );
        claim_I1(I,Nisynch);
        claim_I2(I,Niagree);
        claim_I3(I,Secret, kir);
        claim_I5(I,Empty, (Fresh,kir));
    }    
    
    role R
    {
        var ni: Nonce;
        fresh nr,nr2: Nonce;
        fresh kir: SessionKey;

        recv_1(I,R, I,{ni}k(I,R) );
        send_2(R,I, {ni,nr}k(I,R) );
        recv_3(I,R, {nr}k(I,R) );
        send_4(R,I, {kir,nr2,ni}k(I,R) );
        claim_R1(R,Nisynch);
        claim_R2(R,Niagree);
        claim_R3(R,Secret, kir);
        claim_R5(R,Empty, (Fresh,kir));
    }
}