2Questions2.1 Q1For this question, every encryption scheme satisfies complete correctness.Security is for a single message.2.1.1ALet h1, h2 be negligible functions (that are never equal to zero). Prove ordisprove:1. 1 is negligible as well.2. h1 · h2 is negligible as well.2.1.2 ВWe will define a variation of OTP with a key length k = k||k2 where |k1| =|k2| and M = C = {0,1}10, K = 0, 120. The encryption function :Enc(k = k1||k2, m) = m k1 e k2Complete the decryption algorithm. Prove that the scheme satisfies per-fect correctness and perfect secrecy.2.1.3We will define a variation of OTP with M = {0, 1}10, C = {0, 1}1', K =0,110 Where the encryption algorithm is defined as:{ (me k, 1)(т,0)if k ¢ {0lº, 1º}Enc(k, m)otherwise2Complete the decryption algorithm. Specify for which e the scheme sat-isfies e statistical security. Prove it is the correct e.

In questions with many questions, we must answer the first one.

2 Questions 2.1 Q1 For this question, every encryption scheme satisfies complete correctness. Security is for a single message. 2.1.1 A Let h1, h2 be negligible functions (that are never equal to zero). Prove or disprove: 1. is negligible as well. 2. h h2 is negligible as well.

2 Questions 2.1 Q1 For this question, every encryption scheme satisfies complete correctness. Security is for a single message. 2.1.1 A Let h1, h2 be negligible functions (that are never equal to zero). Prove or disprove: 1. is negligible as well. 2. h h2 is negligible as well.

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

See similar textbooks

Similar questions

Consider the following encryption scheme for a block cipher (using the notationfrequently used in class).y1 = ek(x1), y2 = ek(x1 ⊕ x2), y3 = ek(x1 ⊕ x2 ⊕ x3), etc.a. Describe the corresponding decryption scheme.b. Can encryption and/or decryption be run in parallel for this scheme?c. Taking into account that the operation of XOR is cheap, determinewhether or not this scheme improves on ECB mode or not
1. Suppose that a symmetric cryptosystem with a 32-bit key length is used to encrypt messages written in English and encoded in ASCII. Given that keys are short, an attacker is using a brute-force exhaustive search method to decrypt a ciphertext of t bytes. Estimate the probability of uniquely recovering the plaintext corresponding to the ciphertext for the following values of t: 8, 64, 512. 2. Suppose that you are a computer virus writer; hence, you know that you need to store a copy of the code for your virus inside the virus itself. Moreover, suppose you know that a security administrator is also aware of this fact and will be using it to detect the presence of your virus in operating systems files. Explain how you can hide the embedded copy of your virus so that it is difficult for the security administrator to find it.
Consider the following encryption scheme for a block cipher (using the notationfrequently used in class).y1 = ek(x1 ⊕ IV), y2 = ek(x2), y3 = ek(x3), etc.a. Suppose IV is a block consisting entirely of zeros. Which mode ofoperation does the described mode reduce to?b. Describe the corresponding decryption scheme.c. Can encryption and/or decryption be run in parallel for this scheme?
Q. Consider the Elliptic Curve with given parameters. Answer the following questions ECC a. What would be a public and private key for given elliptic curve? b. Why ECC is prominent among public key cryptographic algorithms? Write benefits of using ECC instead of any other PKI based algorithm. c. Explain purpose of following ECC based protocols. 1. ECDSA, 2. ECDH, 3. ECIES, 4. ECMQV
Let Π = (Gen,Enc,Dec) be a private-key encryption scheme that has indistinguishable en- cryptions in the presence of an eavesdropper. Which of the following encryption schemes are also necessarily secure against an eavesdropper? If you think a scheme is secure, sketch a proof, if not, provide a counterexample. Here, for a bit string s, parity(s) is 1 if the number of 1’s in s is odd, and 0 otherwise. The || symbol stands for concatenation. So, for strings if x = 00 and y = 11, x||y = 0011. (a) Enc1k(m) = 0||Enck(m)(b) Enc2k(m) = Enck(m)||parity(m) (c) Enc3k(m) = Enck(m)||Enck(m)(d) Enc4k(m) = Enck(m)||Enck(m + 1). Here think of m as an integer. Please type answer note write by hend.
1.Give the decryption of the following messages that have been encrypted with the key 4551. You should get readable messages. a. RTYAWJHVVJ b. WYFUMXYJGX c. VTRFS_NMPJEJPQNOSNX 2.Say you obtain a ciphertext of an English sentence encrypted with an unknown key using the same four-digit shift scheme as problems 8 and 9. For a brute-force attack, what is the maximum number of keys would you have to test?
2.(a) Consider the use of OTP. Let m be an arbitrary message to be encrypted and c be a given ciphertext in the ciphertext space. How many possible keys with which m can be mapped to c, i.e., f(m,k)=c? None 1 2 The size of the key space Depends on m (b) 3^(-n) is negligible. True or false? (c) n^(-100) is negligible. True or false?
Consider the case of Alice sending a message, m, to Bob. Both Alice and Bob use public key cryptography and each has a public and private key as described in the text. The figure attached below shows the operations that Alice must perform to provide confidentiality, authentication, and integrity when sending a message to Bob over the network. We can use either symmetric key or public key cryptography to encrypt a message. For our purposes, either technique will encrypt the message, and applying both doesn't make it "more secure". Also, we can assume that the session key would remain a secret so the fact that it is discarded does not make it "more secure". Why do we use a session key, Ks, instead of relying only on public key Cryptography? In other words, why do we use both public key and symmetric key cryptography?
1. (a) Suppose you are given an ElGamal encryption of an unknown plaintext M ∈G. Show how to construct a different ciphertext that also decrypts to the same M. (b) Suppose you are given two ElGamal encryptions, of unknown plaintexts M1,M2 ∈G. Show how to construct a ciphertext that decrypts to their product M1 ·M2
B has just received the following message, which represents a cryptographic data object:{({(KPbB)KPrS mod KPbS}K1,{|(NB, NA, {{({K2}KPbB, NS)}(G1)KPrA mod NA}K1, {|{({G3}(KPbA)KPrS mod KPbS, G2)}K1|}KPrB)|}KPrA)}KBSThe following explains various terms in this object and some of the abbreviations used:• {M}K represents the encryption of some message/data M using the key K• {|M|}K represents the digital signing of some message/data M using the key K• NX represents a nonce (i.e. a fresh and possibly random number used once only) generated by X• KpbX represents the public part of the key pair presumably owned by X• KprX represents the private part of the key pair presumably owned by X• KAB represents a symmetric key shared between A and B• K (or K1, K2, K3 etc.) represents some arbitrary key with no assumptions about its scope• M represents some alphanumeric/textual message with no assumptions• G1, G2, G3 etc. are prime numberswhich of the following sets of keys, nonces, numbers, and…
One potential limitation of a digital signature is that for a given signature σ of a message m corresponding to a public key pk, one could generate a pk', sk' that produces a signature σ' for m, such that σ' = σ. Given a signing function S, a verification function V, that each takes corresponding private and public keys for generating and verifying a signature and is vulnerable to these duplicate keys, please generate S' and V' that are immune to a duplicate keys attack.
1. Assume an 8-letter password from the 95 printable ASCII characters is used in acomputer system.a. If passwords are chosen by the users, what is the total password population? What isthe probability of an adversary guessing a password correctly?b. If passwords are generated automatically by a pseudorandom number generator,what is the total password population? What is the probability of an adversary guessinga password correctly? 2.Explain why, for the biometric authentication protocols, the biometric capture device isauthenticated in the case of static biometric but not authenticated for a dynamic biometric.