ibe-ns.spdl

// 12/05/06
// S. Mauw
// Using Identity Based Encryption primitive to make NSL authentication.
// The only requirement on the server communications is that the
// sending of the private key is secret.

const ibepublic: Function; //publicly known key construction from server
                           //parameters and recipient name
secret ibesecret: Function;//secret key determined by server for recipient
const param: Function;     //public security parameter of server
inversekeys (ibepublic,ibesecret);

protocol ibe(I,R,S)
{
	role I
	{
                fresh ni: Nonce;
                var nr: Nonce;

//Note that we are not interested in the order of server messages.
	        recv_!1(S,I, param(S) );
                send_3(I,R, {I,ni}ibepublic(param(S),R) );
                recv_4(R,I, {ni,nr,R}ibepublic(param(S),I) );
                send_5(I,R, {nr}ibepublic(param(S),R) );


                claim_i1(I,Secret,ni);
                claim_i2(I,Secret,nr);
                claim_i3(I,Niagree);
                claim_i4(I,Nisynch);
	}	
	
	role R
	{
                var ni: Nonce;
                fresh nr: Nonce;

	        recv_!2(S,R, {ibesecret(param(S),R)}pk(R) );
                recv_3(I,R, {I,ni}ibepublic(param(S),R) );
                send_4(R,I, {ni,nr,R}ibepublic(param(S),I) );
                recv_5(I,R, {nr}ibepublic(param(S),R) );

                claim_r1(R,Secret,ni);
                claim_r2(R,Secret,nr);
                claim_r3(R,Niagree);
                claim_r4(R,Nisynch);
	}

	role S
	{
		recv_!0(S,S, R,S);			// workaround for the fact that R & S are roles, so Scyther should not jump to conclusions (remove it and see what happens)
	        send_!1(S,I, param(S) );
	        send_!2(S,R, {ibesecret(param(S),R)}pk(R) );

                claim_s1(S,Secret,ibesecret(param(S),R));
	}
}

compromised ibesecret(param(Eve),Alice);
compromised ibesecret(param(Eve),Bob);
compromised ibesecret(param(Eve),Carol);