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

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# 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)
# In order to overcome this a 'dummy' role X has been hadded that recrypts
# a given term crypted with k(I,R) with k(R,I)
#
# 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;
const Fresh: Function;
protocol swapkey(X)
{
# Protocol added to work around the symmetry problems where k(I,R) != k(R,I)
role X
{
var I,R: Agent;
var T:Ticket;
read_X1(X,X,I,R,{T}k(I,R));
send_X2(X,X,{T}k(R,I));
}
}
protocol andrewConcrete(I,R)
{
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role I
{
const ni: Nonce;
var nr: Nonce;
var kir: SessionKey;
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send_1(I,R, I,ni );
read_2(R,I, {ni,kir}k(I,R) );
send_3(I,R, {ni}kir);
claim_I1(I,Secret,kir);
claim_I2(I,Nisynch);
claim_I3(I,Empty,(Fresh,kir));
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read_6(R,I, nr);
}
role R
{
var ni: Nonce;
const nr: Nonce;
const kir: SessionKey;
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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_R1(R,Secret,kir);
claim_R2(R,Nisynch);
claim_R3(R,Empty,(Fresh,kir));
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}
}
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);