scyther/spdl/SPORE/needham-schroeder.spdl

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# Needham Schroeder Public Key
#
# Modelled after the description in the SPORE library
# http://www.lsv.ens-cachan.fr/spore/nspk.html
#
#
# Note:
# The modelling in SPORE includes a server to distribute the public keys
# of the agents, this is not necessary and it allows for attacks against
# synchronisation and agreement, because the keys that the server sends
# out can be replayed.
secret pk: Function; # For some reason SPORE models it such that the agents
# do not know the public keys of the other agents
secret sk: Function;
inversekeys(pk,sk);
protocol needhamschroederpk(I,R,S)
{
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role I
{
const Ni: Nonce;
var Nr: Nonce;
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send_1(I,S,(I,R));
read_2(S,I, {pk(R), R}sk(S));
send_3(I,R,{Ni,I}pk(R));
read_6(R,I, {Ni, Nr}pk(I));
send_7(I,R, {Nr}pk(R));
claim_I1(I,Secret,Ni);
claim_I2(I,Secret,Nr);
claim_I3(I,Nisynch);
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}
role R
{
const Nr: Nonce;
var Ni: Nonce;
read_3(I,R,{Ni,I}pk(R));
send_4(R,S,(R,I));
read_5(S,R,{pk(I),I}sk(S));
send_6(R,I,{Ni,Nr}pk(I));
read_7(I,R,{Nr}pk(R));
claim_R1(R,Secret,Nr);
claim_R2(R,Secret,Ni);
claim_R3(R,Nisynch);
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}
role S
{
read_1(I,S,(I,R));
send_2(S,I,{pk(R),R}sk(S));
read_4(R,S,(R,I));
send_5(S,R,{pk(I),I}sk(S));
}
}
const Alice,Bob,Simon,Eve: Agent;
untrusted Eve;
const ne: Nonce;
compromised sk(Eve);
compromised pk(Eve);
compromised pk(Simon); # Needed because SPORE only assumes agents know their
# own public key and that of the server
# General scenario, 2 parallel runs of the protocol
run needhamschroederpk.I(Agent,Agent,Simon);
run needhamschroederpk.R(Agent,Agent,Simon);
run needhamschroederpk.S(Agent,Agent,Simon);
run needhamschroederpk.I(Agent,Agent,Simon);
run needhamschroederpk.R(Agent,Agent,Simon);
run needhamschroederpk.S(Agent,Agent,Simon);