A KDC: IDA IDB|N₁
KDCA:
A →B:
B-A:
E(K. [Ks|| IDB|| N₁ E(K₁. [KsIDA)))
E(Kb. [KsIDA])
E(KS, N₂) A→B: E(Ks. f(N₂))
a. Explain the protocol.
b. Can you think of a possible attack on this protocol? Explain how it can be done.
c. Mention a possible technique to get around the attack-not a detailed mechanism,
just the basics of the idea.
Note: The remaining problems deal with a cryptographic product developed by IBM,
which is briefly described in a document at this book's Web site in IBMCrypto.pdf.
Try these problems after reviewing the document.
Fig: 1