Answered: Design a protocol based on a shared…

Design a protocol based on a shared secret key to allow them to authenticate each other; • Explain the limitation of using the shared secret key in this context

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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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?
2. Recall the concept of Physically Unclonable Functions, which are an importantcomponent of hardware based security. Here is a simple scenario and simple protocol usingPUFs for authenticating a tag. In the protocol below, the Reader stores ALL possiblecombinations of Challenge-Response pairs for every tag it needs to authenticate. Duringauthentication, the Reader broadcasts the ID of the tag, and a greeting (Gn ). Every tag maysee this message, but only the one with the right ID will process the message. The right tagwith the ID in the message will then feed the greeting to its PUF and compute the responseSn. The response is then sent to the Reader. This should be clear from the Figure below. Forthe next round of authenticating the same Tag, the process repeats with a new Greeting(G n+1 ). Since the Reader has the responses, authentication is straightforward. Recall thatChallenges and Responses are typically 128 or 256 bit strings for RFIDs.From the protocol, and class, it should be…
2. Suppose that Bob's public key is (p, a, ae) = (7481, 6, 5979). Alice receives the signed message (x, S1, S2) = (478, 1723, 7045) from Bob. Should she accept it?
The hacker group Desdeia tries to break our old weak cipher which we used for the communication with the Duchess of Ligovia. It's generally known that an actual breaking of the cipher needs the reviewing a huge amount of variants which probably lasts a couple of months. Additionally we know that the reviewing of different variants needs always the same server resource. Using our intelligence sources we tried to get some information about the actual progress of breaking, but we got only some fragments: • The hacker group Desdeia uses for breaking their powerful four-core server which resources are fully dedicated to breaking process. . The actual breaking process began exactly at noon, but we don't know, on which day. . By the noon of 2nd of April, already 648,467,673 variants were successfully reviewed. Exactly at this noon, when the breaking process was already lasted for 19 days, it was attempted to double the server speed. The doubling itself was failed, but instead of it there was…
What are the potential limitations of Electronic Code Book (ECB)? If one ciphertext block is corrupted during the transmission, all subsequent ciphertext blocks cannot be decrypted unless until corrupted block is successfully retransmitted. Repetitive information contained in the plaintext may show in the ciphertext, if aligned with blocks. If the same message (e.g., an SSN) is encrypted (with the same key) and sent twice, their ciphertexts are the same. It needs an initialization vector to operate.
A secure email system is expected to provide confidentiality, sender's non-repudiation, and message integrity. Alice uses three keys to achieve this goal. The three keys are Alice's private key (KA), Bob's public key (Kg), and a randomly generated symmetric key (Ks). The encryption procedure is shown below: How can Bob 1) decrypt the data, 2) verify the message's integrity, and 3) verify the sender's non-repudiation? Describe the detailed steps (including the formulas) and show your work. KA m H(-) KA( m I am using SHA-256 KA(H(M)) Ks() KB(*) K Ks K.(m, KA(H(m)) + + KB(Ks) Internet 34
. Q: There is no authentication in the Diffie-Hellman key-exchange protocol. By exploiting this property, a malicious third party, Chuck, can easily break into the key exchange taking place between Alice and Bob, and subsequently ruin the security. Explain how this would work.
Pretend you are Alice and have agreed with Bob to carry out Diffie-Hellman key exchange with parameters p = 23 and g = 5. You may use a calculator to answer the following, but write down and label all the quantities you use. Assume you choose the secret random value x = 19. Compute the value gx (mod p) that you will send to Bob. In the protocol, you receive the value gy = 18 from Bob. Compute your shared secret value. Now pretend you are an eavesdropping adversary. From g, p and gy, find Bob’s secret y (it’s possible!) Describe how you found the value in part (c), and comment on how this reflects the security of Diffie-Hellman key exchange.
Alice needs to transmit a 48-bit message using a 47-bit key. Suggest a scheme that is perfectly secure.
Bob is trying to send a secure message to Alice. By generating these ciphertexts: C1 = Epub_A(P), C2 = Epriv_B(C1), what security property could be achieved?
Alice and Bod have decided to use a symmetric encryption algorithm. They have some assumptions about their messages:- Messages only contain capital letters (i.e. A to Z)- The length of their shared key must be greater than or equal to the length of the plaintext- They assign each letter a number as follows: (A,0), (B,1), (C,2), (D,3),…, (Z,25)Their algorithm combines the key and the message using modular addition. The numerical values of corresponding message and key letters are added together, modulo 26. For example, if the plain text is “HELLO” and the key is “SECRET” then the encrypted message is calculated as following:Since the length of the plaintext is 5, we just need the first 5 letters of the key (i.e. “SECRE”), then for each letter, we should add corresponding letters in both the plaintext and the key modulo 26.Plaintext: H (7) E (4) L (11) L (11) O (14)Key: S (18) E (4) C (2) R (17) E(4)Cipher: Z (25) I (8) N(13) C(2) S (18) Write a program in Python, C/C++ or JavaScript to…