usertype Sessionkey; const pk: Function; secret sk: Function; inversekeys (pk,sk); protocol sophkx(I,R) { role I { const ni: Nonce; const kir: Sessionkey; var nr: Nonce; send_1(I,R, ni, {I,kir}pk(R) ); read_2(R,I, {ni}kir ); claim_4(I,Secret,kir); } role R { var ni: Nonce; var kir: Sessionkey; const nr: Nonce; read_1(I,R, ni, {I,kir}pk(R) ); send_2(R,I, {ni}kir ); } } const Alice,Bob,Eve: Agent; untrusted Eve; const nc: Nonce; const ke: Sessionkey; compromised sk(Eve); run sophkx.I(Agent,Agent); run sophkx.R(Agent,Agent); run sophkx.I(Agent,Agent);