Security and Internet Commerce. Chapter 27. Security in Transaction Systems. Security is essential in many transaction processing applications Authentication Is the user who he says he is? Authorization What is an authenticated user allowed to do? Only cashiers can write cashier’s checks
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ciphertext = Ksender[plaintext]
Ksender = Kreceiver
M = K[K[M]]
abc xza, def tyy, ghi rew, ...
abc bca, def efd, ghi hig, ...
KuPub and KuPri
M = KuPri[KuPub[M]]
e*d 1 (mod (p-1)*(q-1))
C = M e (mod N)
M = C d (mod N)
KPub[KPri[M]] = M
|f (M) | << |M |
M1, M2, M3
M4, M5, M6
M7, M8, M9
v1 v2 v3
Sets have roughly equal size.
Elements of a set are unrelated.
KC, KS[KSess C-S , S, LT] --- C can decrypt this
KS, KS[KSess C-S , C, LT] --- The ticket; C cannot decrypt this
M1: (C, S)
M3: (ticket, authenticator, arguments)
KC, AS[KSess C-TGS , TGS, LT] - session keyfor TGS
KTGS, AS[KSess C-TGS , C, LT] - tkt for service from TGS
KSess,C-TGS[KSess C-S , S, LT] - session key for S
KS, AS[KSess C-S, C, LT] - ticket for S
m1: KGPub[Trans_id, credit_card_info, $_amount]
m2: KMPub[Trans_id, $_amount, desc]
Dual signature: f(m1), f(m2), KCPri[f(f(m1)*f(m2))]
m4: KGPub[Trans_id, $_amount, KMPri[f(Trans_id, $_amount)]]
b-1(KjPri[b(n)]) = b-1(b(KjPri[(n)])) = KjPri[n]
u*u-1 =1 (mod N)
KjPub[u] * n (mod N)
sr = KjPri[KjPub[u]*n]
KjPri[n] = u-1 * sr (mod N)