Note: The notation from this problem is from Understanding Cryptography by Paar and Pelzl. Suppose you have an LFSR with 6 state bits. The first 12 bits of output produced by this LFSR are 100000110110 = so s1 S2 S3 S4 S5 S6 S7 Sg S9 S10 S11 · The first bit produced is the leftmost bit and the bit most recently produced is the rightmost bit. a) What is the initial state of the LFSR? Please enter your answer as unspaced binary digits (e.g. 010101 to represent S5 = 0, s4 = 1, s3 = 0, s2 = 1, s1 = 0, so = 1). b) What are the tap bits of the LFSR? Please enter your answer as unspaced binary digits (e.g. 010101 to represent P5 = 0, p4 = 1, P3 = 0, p2 = 1, p1 = 0, po = 1).

Note: The notation from this problem is from Understanding Cryptography by Paar and Pelzl. Suppose you have an LFSR with 6 state bits. The first 12 bits of output produced by this LFSR are 100000110110 = so s1 S2 S3 S4 S5 S6 S7 Sg S9 S10 S11 · The first bit produced is the leftmost bit and the bit most recently produced is the rightmost bit. a) What is the initial state of the LFSR? Please enter your answer as unspaced binary digits (e.g. 010101 to represent S5 = 0, s4 = 1, s3 = 0, s2 = 1, s1 = 0, so = 1). b) What are the tap bits of the LFSR? Please enter your answer as unspaced binary digits (e.g. 010101 to represent P5 = 0, p4 = 1, P3 = 0, p2 = 1, p1 = 0, po = 1).

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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The notation from this problem is from Understanding Cryptography by Paar and Pelzl. We conduct a known-plaintext attack against an LFSR. Through trial and error we have determined that the number of states is m=4m=4.The plaintext given by 01001011=x0x1x2x3x4x5x6x701001011=x0x1x2x3x4x5x6x7 when encrypted by the LFSR produced the ciphertext 11010110=y0y1y2y3y3y5y6y711010110=y0y1y2y3y3y5y6y7. What are the tap bits of the LFSR? Please enter your answer as unspaced binary digits (e.g. 0101 to represent p3=0,p2=1,p1=0,p0=1p3=0,p2=1,p1=0,p0=1).
Give encryption or decryption of these hexadecimal messages using the one-time pad algorithm, giving the result in hexadecimal also. You may wish to convert to binary first. a. m = 0xdeadbeef, K = 0x4ea04002, c = ? b. c = 0x84848484, K = 0xffffffff, m = ? c. c = 0x104557ce, K = 0xdabbad00, m = ?
Question KNh Similar to Problem 3.4 in the textbook(• C. Paar and J. Pelzl, Understanding Cryptography, Springer, 2009. ISBN 978-3-642-04100-6.): What is the output of the a round of the DES f-function when the 48-bit output of the expansion function and the 48-bit round key are both all ones? Write first (in binary) the outputs of the S-boxes:S1(0)=S2(0)=S3(0)=S4(0)=S5(0)=S6(0)=S7(0)=S8(0)=Next, write (in Hexadecimal) the output of the P permutation withing the f-function: ( )
a. Compute CBC-MAC for a message of 16 bits, “8642” (in Hexa). Assume a block size of 8 bits with an IV=F1 (in hexa). For simplicity, assume the encryption to be a simple XOR of the key with the plaintext. Let the encryption key be B4 (in Hexa). (Hint: Divide the message into blocks of 8 bits each; XOR each block with the previous cipher output; then encrypt this with the key. For the first block, XOR it with IV. Details in pages 325-326 Ch.12 of the textbook) b. Suppose Alice computes the Secret prefix MAC (page 322: secret prefix MAC(x) = h(key || x)) for the message ”AM” (in ASCII) with key “G” (in ASCII) that both Alice and Bob know. The hash function that is used is h(x1x2x3)= g(g(x1 XOR x2) XOR x3 ) where each xi is a character represented as 8 bits, and g(x) is a 8-bit string that is equal to the complement of bits in x. For example, g(10110011) = 01001100. The MAC is 8 bits. (8-bit ASCII representation of the characters is given below.) What is the Secret prefix MAC…
A shortcoming of using an elliptic curve E(Fp) for cryptography is the fact that it takes two coordinates to specify a point in E(Fp). However, as discussed briefly at the end of Sect. 6.4.2, the second coordinate actually conveys very little additional information.(b) Alice and Bob decide to use the prime p = 1123 and the elliptic curveE : Y2 = X3 + 54X + 87.Bob sends Alice the x-coordinate x = 278 and the bit β = 0. What point is Bob trying to convey to Alice? What about if instead Bob had sent β = 1?
To prevent the tapping and use of information on a wireless network which has brought untold mistrust amongst the directors of Okonko Systems, you suggested that every message that is transmitted should go through the following: A systematic two left bit shift; After “a” above, the algorithm f[(6m +2) + k] mode 13 should be applied to the cipher text, where m is the message and k =9 is a key; After “b” above, perform a systematic right bit shift to the new cipher; The message should then be transmitted. If on a trial basis, the message is “genomics” Use the mono – alphabetic letters where a = 0, b = 1, ….z = 25 to find the cipher that would be transmitted
We use DES in cipher feedback mode (CFB) to encrypt a plaintext m = m1m2 ...m100 into a ciphertext c1c2 ...c100, where each mi is 8-bit long. The ciphertext is sent to Bob. If c15 and c25 are missing and c8 and c88 are received as c8' and c88' wrongly, what mi’s can B compute correctly from the received ciphertext?
Encrypt the message " MATH " by translating the letters into numbersand then applying the encryption function given, and then translating the numbers back into letters.(a) f(p)=(17p+5) mod 26 _____ (b) f(p)=(15p+14) mod 26 ___ (c) f(p)=(19p+5) mod 26 ___Use A=0,B=1,C=2,D=3,E=4,F=5,G=6,H=7,I=8, J=9,K=10,L=11,M=12,N=13,O=14,P=15,Q=16,R=17, S=18,T=19,U=20,V=21,W=22,X=23,Y=24,Z=25
Compute CBC-MAC for a message of 16 bits, “ABCD” (in Hexa). Assume a block size of 8 bits with an IV=C9 (in hexa). For simplicity, assume the encryption to be a simple XOR of the key with the plaintext. Let the encryption key be D8 (in Hexa). (Hint: Divide the message into blocks of 8 bits each; XOR each block with the previous cipher output; then encrypt this with the key. For the first block, XOR it with IV.
A cryptography student has accidentally used the same keystream to encrypt two different messages, M1M1 and M2M2. We know that the ciphertexts are C1=0x4ab397cf20db1ce0C1=0x4ab397cf20db1ce0 and C2=0x2f7fded503744af5C2=0x2f7fded503744af5. We also happen to know that M1=0xbc66dac8daeee8e2M1=0xbc66dac8daeee8e2. a) What is M2M2 in hexadecimal? Please give your answer a leading 0x and use lowercase letters only. b) What is the keystream? Please give your answer a leading 0x and use lowercase letters only. Hint: These are all 8 byte numbers and will fit in an unsigned long type on most systems.
Suppose Data Encryption Standard (DES) is used to encrypt the following 64-bit block of plaintext: 6 3 F A C 0 D 0 3 4 D 9 F 7 9 3 Given the initial 64-bit key is: 1 C 5 8 7 F 1 C 1 3 9 2 4 F E F Expand R0 to get E[R0]
Suppose we will use Advanced Encryption Standard (AES) to encrypt a block of plaintext and the known round key for round 7 is: B5 8D BA D2 31 2B F5 60 7F 8D 29 2F EA D2 73 21 What is the third word (i.e. the third 4 bytes) of the round key for round 8?