scyther/spdl/otwayrees.spdl

secret const k : Function;

/* Version from the Spore Librairy
   http://www.lsv.ens-cachan.fr/spore/otwayRees.html
*/

usertype String, SesKey, Ticket, Server;

protocol otwayrees(A,B,S)
{
	role A
	{
		const na : Nonce;
		const M : String;
		var nb : Nonce;
		var kab : SesKey;

		send_1(A,B, M,A,B, { na,M,A,B }k(A,S) );
		read_4(B,A, M, { na,kab }k(A,S) );

		claim(A, Secret,kab);
	}

	role B
	{
		var na : Nonce;
		var M : String;
		const nb : Nonce;
		var kab : SesKey;
		var t1,t2 : Ticket;

		read_1(A,B, M,A,B, t1 );
		send_2(B,S, M,A,B, t2, { nb,M,A,B }k(B,S) );
		read_3(S,B, M, t2, { nb,kab }k(B,S) );
		send_4(B,A, M, t2 );

		claim(B, Secret,kab);
	}

	role S
	{
		var na,nb : Nonce;
		var M : String;
		const kab : SesKey;
		
		read_2(B,S, M,A,B, { na,M,A,B }k(A,S), { nb,M,A,B }k(B,S) );
		send_3(S,B, M, { na,kab }k(A,S) , { nb,kab }k(B,S) );
	}
}

const Alice, Bob, Eve: Agent;
const Simon: Server;

untrusted Eve;
compromised k(Eve,Simon);

run otwayrees.A(Alice, Agent, Simon);
run otwayrees.B(Agent, Bob, Simon);
run otwayrees.S(Agent, Agent, Simon);

run otwayrees.A(Agent, Agent, Simon);
run otwayrees.B(Agent, Agent, Simon);
run otwayrees.S(Agent, Agent, Simon);