**** Protocol: Needham-Schroeder-Lowe ****
**** Unsafe States ****
[unsafe([step3(A,tuple(B,_,C)),mem(B)],{A>0,C>0}),unsafe([step3(A,tuple(_,D,C)),mem(D)],{A>0,C>0}),unsafe([step4(C,tuple(B,_,A)),mem(B)],{A>0,C>0}),unsafe([step4(C,tuple(_,D,A)),mem(D)],{A>0,C>0})].

**** Potential Attacks ****