scyther/spdl/ns-symmetric-amended.spdl

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/*
* Needham-Schroeder symmetric
* Amended version (from Sjouke's interpret.)
*/
/* symmetric */
usertype SessionKey;
secret k: Function;
/* agents */
const a,b,e: Agent;
/* untrusted e */
untrusted e;
const ne: Nonce;
const kee: SessionKey;
compromised k(e,e);
compromised k(e,a);
compromised k(e,b);
compromised k(a,e);
compromised k(b,e);
/* {}x used for public (invertible) function modeling */
usertype PseudoFunction;
const succ: PseudoFunction;
usertype Ticket;
protocol nssymmetricamended(A,S,B)
{
role A
{
const na: Nonce;
var T1: Ticket;
var T2: Ticket;
var kab: SessionKey;
var nb: Nonce;
send_1(A,B, A );
read_2(B,A, T1 );
send_3(A,S, A,B,na,T1 );
read_4(S,A, { na,B,kab,T2 }k(A,S) );
send_5(A,B, T2 );
read_6(B,A, { nb }kab );
send_7(A,B, { {nb}succ }kab );
claim_8(A, Secret, kab);
}
role S
{
const kab: SessionKey;
var na: Nonce;
var nb: Nonce;
read_3(A,S, A,B,na, { A,nb }k(B,S) );
send_4(S,A, { na,B,kab, { kab,A }k(B,S) }k(A,S) );
}
role B
{
var kab: SessionKey;
const nb: Nonce;
read_1(A,B, A );
send_2(B,A, { A,nb }k(B,S) );
read_5(A,B, { kab,A }k(B,S) );
send_6(B,A, { nb }kab );
read_7(A,B, { {nb}succ }kab );
claim_9(B, Secret, kab);
}
}