secret fresh 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
	{
		fresh na : Nonce;
		fresh M : String;
		var kab : SesKey;

		send_1(A,B, M,A,B, { na,M,A,B }k(A,S) );
		recv_4(B,A, M, { na,kab }k(A,S) );

		claim_5(A, Secret,kab);
		claim_5b(A, Niagree);
		claim_5c(A, Nisynch);
	}

	role B
	{
		var M : String;
		fresh nb : Nonce;
		var kab : SesKey;
		var t1,t2;

		recv_1(A,B, M,A,B, t1 );
		send_2(B,S, M,A,B, t1, { nb,M,A,B }k(B,S) );
		recv_3(S,B, M, t2, { nb,kab }k(B,S) );
		send_4(B,A, M, t2 );

		claim_6(B, Secret,kab);
		claim_6a(B, Niagree);
		claim_6b(B, Nisynch);
	}

	role S
	{
		var na,nb : Nonce;
		var M : String;
		fresh kab : SesKey;
		
		recv_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;