EBK COMPUTER NETWORKING
7th Edition
ISBN: 8220102955479
Author: Ross
Publisher: PEARSON
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Chapter 8, Problem R11RQ
Program Plan Intro
Hash Function:
Any function that can be used to map data of arbitrary size to data of a fixed size is called a hash function.
Hash functions provide message integrity as it is computationally infeasible to find any two messages with the same hash.
Hashing:
Hashing is a data structure technique that is used to index and retrieve items in a
Given information:
In a Message Authentication Code (MAC), the sender sends
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Msg3. B→A : B, N1, Ks, Message2, h(B, N1, Message2)
Whereas:
h(m) represents the digest of the message (m).
{m}{K} represents the encryption of message (m) using the key (K)
PK is public key
N1 is a random number.
1. What are the main problems in Msg3?
Alice and Bob decided to use HMAC to authenticate the communication between them. They already share a key k for
the MAC scheme. To sign a message M (which is always of an even bit length), the sender parses the message as
M=M_L||M_R, i.e. the message is parsed as a left half and a right half (both halves have equal length), then the sender
computes X-M₁MR (where denotes XOR). The sender then sends M and T=HMACK(X) to the other party. Does this
construction provide existential unforgeability?
Yes
No
The function f(R, K) = P(S(E(R XOR K)) of the DES
cryptographic protocol manipulates different sizes of bit-strings. The bit-string sizes of
P-SEK in this order are:
32-48-48-32
32-32-48 48
48-48-32-32
64-32-32 48
64 48 32-64
SAVE
Chapter 8 Solutions
EBK COMPUTER NETWORKING
Ch. 8 - Prob. R1RQCh. 8 - Prob. R2RQCh. 8 - Prob. R3RQCh. 8 - Prob. R4RQCh. 8 - Prob. R5RQCh. 8 - Prob. R6RQCh. 8 - Prob. R7RQCh. 8 - Prob. R8RQCh. 8 - Prob. R9RQCh. 8 - Prob. R10RQ
Ch. 8 - Prob. R11RQCh. 8 - Prob. R12RQCh. 8 - Prob. R13RQCh. 8 - Prob. R14RQCh. 8 - Prob. R15RQCh. 8 - Prob. R16RQCh. 8 - Prob. R17RQCh. 8 - Prob. R18RQCh. 8 - Prob. R19RQCh. 8 - Prob. R20RQCh. 8 - Prob. R21RQCh. 8 - Prob. R22RQCh. 8 - Prob. R23RQCh. 8 - Prob. R24RQCh. 8 - Prob. R25RQCh. 8 - Prob. R26RQCh. 8 - Prob. R27RQCh. 8 - Prob. R28RQCh. 8 - Prob. R29RQCh. 8 - Prob. R30RQCh. 8 - Prob. R31RQCh. 8 - Prob. R32RQCh. 8 - Prob. R33RQCh. 8 - Prob. P1PCh. 8 - Prob. P2PCh. 8 - Prob. P3PCh. 8 - Prob. P4PCh. 8 - Prob. P5PCh. 8 - Prob. P6PCh. 8 - Prob. P8PCh. 8 - Prob. P12PCh. 8 - Prob. P13PCh. 8 - Prob. P14PCh. 8 - Prob. P18PCh. 8 - Prob. P20PCh. 8 - Prob. P21PCh. 8 - Prob. P22PCh. 8 - Prob. P23P
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