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y(afterw)o(ard.)1158 2315 y Fe(\017)19 b Ff(Programmers)13 b(at)g(one)g(bank)g(did)h(not)f(ev)o (en)g(go)g(to)g(the)1196 2357 y(trouble)j(of)f(setting)h(up)f(master)g(k)o (eys)g(for)g(its)g(encryp-)1196 2398 y(tion)c(soft)o(w)o(are.)16 b(They)10 b(just)h(directed)g(the)g(k)o(ey)g(p)q(oin)o(ters)1196 2440 y(to)g(an)i(area)f(of)g(lo)o(w)g(memory)g(whic)o(h)h(is)f(alw)o(a)o(ys)h (zero)f(at)1196 2481 y(system)k(startup.)28 b(The)17 b(e\013ect)g(of)f(this)h (w)o(as)f(that)h(the)1196 2523 y(liv)o(e)e(and)f(test)g(systems)g(could)i (use)e(the)g(same)g(crypto-)1196 2564 y(graphic)k(k)o(ey)f(dataset,)h(and)f (the)g(bank's)h(tec)o(hnicians)1196 2606 y(found)g(that)f(they)h(could)h(w)o (ork)e(out)g(customer)h(PINs)1196 2647 y(on)e(their)h(test)f(equipmen)o(t.)28 b(Some)17 b(of)f(them)g(used)h(to)1196 2689 y(c)o(harge)c(the)g(lo)q(cal)h (underw)o(orld)g(to)f(calculate)h(PINs)f(on)p eop %%Page: 6 6 bop 100 -34 a Ff(stolen)18 b(cards;)h(when)e(the)g(bank's)g(securit)o(y)h (manager)100 7 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y(or)f(slopp)o(y)h(op)q (erating)g(pro)q(cedures)g(can)e(lea)o(v)o(e)i(the)e(bank)h(ex-)1113 1320 y(p)q(osed.)1158 1399 y Fe(\017)19 b Ff(Most)f(securit)o(y)h(mo)q(dules) h(return)f(a)f(whole)h(range)f(of)1196 1441 y(resp)q(onse)12 b(co)q(des)g(to)g(incoming)i(transactions.)k(A)11 b(n)o(um-)1196 1482 y(b)q(er)g(of)g(these,)g(suc)o(h)h(as)f(`k)o(ey)g(parit)o(y)i(error')e ([VSM])f(giv)o(e)1196 1524 y(adv)n(ance)21 b(w)o(arning)g(that)f(a)g (programmer)h(is)f(exp)q(eri-)1196 1565 y(men)o(ting)14 b(with)f(a)g(liv)o(e) i(mo)q(dule.)j(Ho)o(w)o(ev)o(er,)13 b(few)f(banks)1196 1607 y(b)q(other)g(to)g(write)h(the)f(device)h(driv)o(er)g(soft)o(w)o(are)f (needed)1196 1648 y(to)h(in)o(tercept)h(and)f(act)g(on)h(these)f(w)o (arnings.)1158 1705 y Fe(\017)19 b Ff(W)m(e)11 b(kno)o(w)h(of)f(cases)h (where)g(a)f(bank)i(sub)q(con)o(tracted)g(all)1196 1746 y(or)k(part)h(of)f (its)g(A)m(TM)g(system)h(to)f(a)g(`facilities)j(man-)1196 1788 y(agemen)o(t')f(\014rm,)h(and)g(ga)o(v)o(e)f(this)h(\014rm)f(its)h(PIN)e(k)o (ey)m(.)1196 1829 y(There)13 b(ha)o(v)o(e)h(also)h(b)q(een)f(cases)g(where)f (PIN)h(k)o(eys)g(ha)o(v)o(e)1196 1871 y(b)q(een)j(shared)h(b)q(et)o(w)o(een)f (t)o(w)o(o)g(or)g(more)g(banks.)30 b(Ev)o(en)1196 1912 y(if)18 b(all)h(bank)f(sta\013)g(could)i(b)q(e)d(trusted,)j(outside)f(\014rms)1196 1954 y(ma)o(y)c(not)g(share)g(the)g(banks')h(securit)o(y)g(culture:)21 b(their)1196 1995 y(sta\013)13 b(are)f(not)h(alw)o(a)o(ys)h(v)o(etted,)e(are) h(not)g(tied)g(do)o(wn)g(for)1196 2037 y(life)g(with)g(c)o(heap)h(mortgages,) f(and)h(are)e(more)h(lik)o(ely)i(to)1196 2078 y(ha)o(v)o(e)d(the)g(com)o (bination)i(of)e(y)o(outh,)g(lo)o(w)g(pa)o(y)m(,)g(curiosit)o(y)1196 2120 y(and)j(rec)o(klessness)h(whic)o(h)f(can)f(lead)i(to)e(a)g(no)o(v)o(el)i (fraud)1196 2161 y(b)q(eing)e(conceiv)o(ed)h(and)f(carried)g(out.)1158 2217 y Fe(\017)19 b Ff(Key)e(managemen)o(t)h(is)f(usually)j(p)q(o)q(or.)29 b(W)m(e)18 b(ha)o(v)o(e)f(ex-)1196 2259 y(p)q(erience)i(of)f(a)f(main)o (tenance)j(engineer)g(b)q(eing)f(giv)o(en)1196 2300 y(b)q(oth)d(of)g(the)g (PR)o(OMs)g(in)h(whic)o(h)g(the)f(securit)o(y)h(mo)q(d-)1196 2342 y(ule)11 b(master)f(k)o(eys)h(are)f(stored.)17 b(Although)11 b(dual)h(con)o(trol)1196 2383 y(pro)q(cedures)g(existed)h(in)f(theory)m(,)g (the)f(sta\013)h(had)g(turned)1196 2425 y(o)o(v)o(er)h(since)g(the)g(PR)o (OMs)g(w)o(ere)f(last)i(used,)f(and)g(so)g(no-)1196 2466 y(one)f(had)g(an)o (y)h(idea)g(what)f(to)g(do.)k(The)c(engineer)i(could)1196 2508 y(not)e(only)i(ha)o(v)o(e)f(forged)g(cards;)g(he)f(could)i(ha)o(v)o(e)f(w)o (alk)o(ed)1196 2550 y(o\013)e(with)g(the)f(PR)o(OMs)h(and)h(sh)o(ut)f(do)o (wn)g(all)h(the)e(bank's)1196 2591 y(A)m(TM)i(op)q(erations.)1158 2647 y Fe(\017)19 b Ff(A)o(t)13 b(branc)o(h)i(lev)o(el,)g(to)q(o,)f(k)o(ey)g (managemen)o(t)h(is)g(a)f(prob-)1196 2689 y(lem.)36 b(As)18 b(w)o(e)h(ha)o(v)o(e)h(seen,)g(the)g(theory)g(is)f(that)h(t)o(w)o(o)p eop %%Page: 7 7 bop 100 -34 a Ff(bank)o(ers)21 b(t)o(yp)q(e)g(in)g(one)g(k)o(ey)g(comp)q (onen)o(t)g(eac)o(h,)i(and)100 7 y(these)11 b(are)g(com)o(bined)h(to)f(giv)o (e)g(a)g(terminal)h(master)f(k)o(ey;)100 49 y(the)i(PIN)g(k)o(ey)m(,)g (encrypted)h(under)g(this)g(terminal)h(mas-)100 90 y(ter)e(k)o(ey)m(,)h(is)h (then)f(sen)o(t)g(to)g(the)g(A)m(TM)f(during)j(the)e(\014rst)100 132 y(service)g(transaction)h(after)d(main)o(tenance.)100 178 y(If)g(the)h(main)o(tenance)i(engineer)g(can)e(get)g(hold)i(of)e(b)q(oth)100 220 y(the)g(k)o(ey)g(comp)q(onen)o(ts,)g(he)g(can)g(decrypt)h(the)f(PIN)f(k)o (ey)100 261 y(and)e(forge)g(cards.)16 b(In)10 b(practice,)i(the)d(branc)o(h)i (managers)100 303 y(who)19 b(ha)o(v)o(e)h(custo)q(dy)g(of)f(the)h(k)o(eys)f (are)h(quite)g(happ)o(y)100 344 y(to)14 b(giv)o(e)i(them)f(to)f(him,)i(as)e (they)h(don't)g(lik)o(e)h(standing)100 386 y(around)i(while)h(the)e(mac)o (hine)i(is)f(serviced.)31 b(F)m(urther-)100 427 y(more,)14 b(en)o(tering)i(a)f(terminal)h(k)o(ey)f(comp)q(onen)o(t)h(means)100 469 y(using)21 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269 y(easily)19 b(b)q(e)e(implemen)o(ted)i(the)f(wrong) f(w)o(a)o(y)m(.)29 b(W)m(e)17 b(sa)o(w)1196 311 y(ab)q(o)o(v)o(e)g(ho)o(w)f (writing)i(the)e(PIN)g(to)g(the)g(card)h(trac)o(k)g(is)1196 352 y(useless,)h(unless)g(the)e(encryption)j(is)e(salted)g(with)g(the)1196 394 y(accoun)o(t)d(n)o(um)o(b)q(er)g(or)f(otherwise)h(tied)h(to)e(the)g (individ)q(-)1196 435 y(ual)d(card;)h(there)f(are)f(man)o(y)i(other)f(subtle) g(errors)g(whic)o(h)1196 477 y(can)19 b(b)q(e)g(made)g(in)h(designing)i (cryptographic)f(proto-)1196 518 y(cols,)15 b(and)g(the)f(study)h(of)f(them)g (is)h(a)f(whole)h(discipli)q(ne)1196 560 y(of)d(itself)i([BAN].)e(In)g(fact,) h(there)g(is)g(op)q(en)h(con)o(tro)o(v)o(ersy)1196 601 y(ab)q(out)20 b(the)g(design)i(of)d(a)h(new)g(banking)i(encryption)1196 643 y(standard,)16 b(ISO)f(11166,)h(whic)o(h)g(is)f(already)i(in)e(use)h(b)o(y) 1196 684 y(some)d(2,000)g(banks)h(w)o(orldwide)h([R].)1158 738 y Fe(\017)k Ff(It)f(is)i(also)g(p)q(ossible)i(to)d(\014nd)h(a)f(DES)h(k)o 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