scyther/spdl/SPORE/andrew-ban-concrete.spdl

# BAN concrete Andrew Secure RPC
#
# Modelled after the description in the SPORE library
# http://www.lsv.ens-cachan.fr/spore/andrewBAN2.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:
# The attack mentioned in SPORE is not found because of the property in the
# previous note
#
# Note:
# Read 4 by the Initatior has been placed after the synchronisation claim
# as it allows trivial synchronisation attacks otherwise (the message is 
# completely fresh and can therefore always be replaced by an arbitrary value 
# created by the intruder) which are not considered in SPORE
#

usertype SessionKey;
secret k: Function;

protocol andrewConcrete(I,R)
{
    role I
    {
        const ni: Nonce;
        var nr: Nonce;
        var kir: SessionKey;
        
        send_1(I,R, I,ni );
        read_2(R,I, {ni,kir}k(I,R) );
        send_3(I,R, {ni}kir);
        claim_4(I,Secret,kir);
        claim_5(I,Nisynch);
        read_6(R,I, nr);
    }    
    
    role R
    {
        var ni: Nonce;
        const nr: Nonce;
        const kir: SessionKey;

        read_1(I,R, I,ni );
        send_2(R,I, {ni,kir}k(I,R) );
        read_3(I,R, {ni}kir);
        send_6(R,I, nr);
        claim_7(R,Secret,kir);
        claim_8(R,Nisynch);
    }
}

const Alice,Bob,Eve: Agent;

untrusted Eve;
const ne: Nonce;
const kee: SessionKey;

# This scenario should find the attack in SPORE
# run andrewConcrete.I(Alice,Bob);
# run andrewConcrete.R(Bob,Alice);

# This is the original scenario
run andrewConcrete.I(Agent,Agent);
run andrewConcrete.R(Agent,Agent);
run andrewConcrete.I(Agent,Agent);
run andrewConcrete.R(Agent,Agent);