problemanalysis3

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

Assume there is a Certificate Authority (CA) with a well-known public key. Further assume every user is issued a certificate for his/her public key. For convenience, we use PKu and SKu to represent user’s public key and private key, respectively. Draw diagrams to answer the following questions. a) Suppose Alice wants to send a large secret message M to Bob. Describe how Alice should send M in an authenticated way. b) Assume Bob receives the message sent by Alice. Describe how Bob should process the message. c) Suppose Alice needs to send a number of large secret messages to Bob. Alice would like to avoid signing digital signatures for all these messages. Develop a protocol for Alice and Bob so that all the messages can be sent in a confidential and authenticated way. Briefly describe the intuition of your protocol first and then draw a diagram.

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.

For practical encryption that involves secret message transmission from Alice to Bob, why is the message encrypted with the shared symmetric key rather than Bob's public key? What is the significance of using Bob's public key to encrypt the shared symmetric key?

Cryptography: Alice and Bob are going to establish a secure session key utilizing Diffie-Hellman key exchange. The agreed upon public prime is, 10477, Alice’s secret is 997, Bob’s secret is 1137. The public base is 31.  What is their session key?

igital Signature using the RSA algorithm: Alice is sending an integer value mA = 3 to Bob with RSA signing. Alice's public key and private key are (5, 14) and (11, 14). Alice first releases her public key to public. How to calculate the signature sig(mA).

In his landmark 1949 paper, Communication Theory of Secrecy Systems, Claude Shannon introduced the concept of product ciphers, which are based upon combining two basic methods of introducing randomness into the information being communicated. What are these methods?

Chapter 8: Problem 9 Previous Problem Problem List Next Problem Results for this submission Entered 49 146 Answer Preview Result 49 146 incorrect incorrect At least one of the answers above is NOT correct. (1 point) Alice and Bob are using the ElGamal cipher with the parameters p = 193 and a = = 5. = = Alice makes the mistake of using the same ephemeral key for two plaintexts, x1 and x 2. The eavesdropper Eve suspects that x1 146. She sees the two ciphertexts y1 = 141 and y2 = = 167 in transit; these are the encryptions of x1 and x2, respectively. a) What is the masking key kм? 49 b) What is the plaintext x2 ? 146

Both parts please

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?

Digital Signature using the RSA algorithm:  Alice is sending an integer value mA = 3 to Bob with RSA signing. Alice's public key and private key are (5, 14) and (11, 14). Alice first releases her public key to public. Charlie, an attacker, sends a message mC = 4 to Bob and lets Bob believe mC is from Alice. mC’s digital signature sig(mC) is calculated using Charlie’s private key (7, 15). Show how Charlie computes sig(mC), and how Bob verifies whether it is from Alice or not (hint: Bob will use Alice’s public key).

Is it feasible to produce secret keys for use in cryptographic protocols on a desktop computer using software in such a safe way that they can be utilised, and is it viable to do so on a desktop computer?

Using a connected public key and private key, Alice and Bob may accomplish both secrecy and authentication.

5. Use RSA public-key encryption to decrypt the message 111 using the private keys n = 133 and d = 5.

The security scheme for IEEE 802.11, prior to 11i, was Wired Equivalent Privacy (WEP). WEP assumed all devices on the network share a security key.  The purpose of the authentication scenario is for the STA to prove that it possesses the security key. Authentication proceeds as shown in Figure 24.13 What are the benefits of the authentication scheme? The authentication scheme is incomplete. What is missing and why is it important? What is a cryptographic weakness of this scheme?

4. In the RSA public-key encryption scheme, each user has a public key, e, and a private key, d. Suppose Bob leaks his private key. Rather than generating a new modulus, he decides to generate a new public and a new private key. Is this safe?

PLEASE SHOW ALL THE WORK!! THANKS IN ADVANCE Alice decides to set up an RSA public key encryption using the two primes p = 31 and q = 41 and the encryption key e = 11. You must show all calculations, including MOD- calculations using the division algorithm! (1) Bob decides to send the message M = 30 to her using this encryption. What is the code C that he will send her? (2) What is Alice's decryption key d? Remember that you have to show all your work using the Euclidean algorithm. (3) Alice also receives the message C = 101 from Carla. What was her original message M?

12. One scenario of cryptanalytical attack is "ciphertext only" in which the attacker has only the encoded string. What are the other three scenarios that are important to consider when analyzing the security of a cipher?

Computer Science * Alice and Bob are conducting Diffie-Hellman key exchange with the parameters p = 101 and a = 2. Their parameters are small and we decide to crack the key exchange. Suppose Alice is observed sending public key A = 79 and Bob sends public key B = 26. a) What is Alice's private key? b) What is Bob's private key? c) What is the shared secret? Alice and Bob are using the EIGamal cipher with the parameters p = 29 and a = 2. %3D Their parameters are small and we decide to crack the cipher. Suppose Alice is observed sending public ephemeral key kE 25 and Bob sends public key 3 = 4. %3D Alice is observed transmitting the ciphertext y = 13. a) What is the masking key kM? b) What is the plaintext?

Question 1 a and b show work

1. Perform encryption and decryption using the RSA algorithm for p=3, q=5, e-7, d=3, M=13, where p, q are two prime numbers used to generate modulus n, e is the public key component, d is the private key component and M is the message.

Help please

Question 2:   You are Alice. Bob publishes his ElGamal public key (q, a, ya) = (101, 2, 14). You desire to send the secret message “CALL ME” to Bob. Using the equivalence A = 01, B = 02, and so on up to Z = 26, you encode the message into the number 03 01 12 12 13 05. Regarding each of these two-digit numbers as a plaintext block, compute the message that you will send to Bob using his public key. This requires you to pick a “random” number k; use k = 32.   You are Bob. You get a message from Alice. You like Alice a lot, so you are eager to read the message. Use your secret key (101, 2, 10) to decrypt Alice’s message. Notice that you don’t need to know what value of k Alice used in order to do this.

What are the potential limitations of Electronic Code Book (ECB)?   Question 13 options:   If one ciphertext block is corrupted during the transmission, all subsequent ciphertext blocks cannot be decrypted unless until corrupted block is successfully retransmitted.    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.   Repetitive patterns contained in the plaintext may be revealed in the ciphertext, if aligned with blocks.

Exercise 1 - Review (Substitution Cipher) 1. The ciphertext below was encrypted using a substitution cipher. Decrypt the ciphertext without knowledge of the key.   ywkdmkmj lbmbr nkwerulwbt orkrumh lmkbjl wl m surywru pwopru-rdnvmbwjk wklbwbnbwjk vjyywbbrd bj jxxruwko mxxjudmlhr mkd ravrhhrkb rdnvmbwjk bj wbl vhwrkbl xujy mvujll ywkdmkmj mkd jbpru krwopljuwko urowjkl. bpr nkwerulwbt pml lmvvmhmnurmbr mkd sjlb-lmvvmhmnurmbr drourr sujoumyl wk mouwvnhbnur, xwlpruwrl, rkowkrruwko, rdnvmbwjk, lnlwkrll mdywkwlbumbwjk mkd mvvjnkbmkvt, kmbnumh lvwrkvrl mkd ymbprymbwvl, mkd ljvwmh lvwrkvrl mkd pnymkwbwrl, oumdnmbr lbndwrl, mkd hmc. m knylru jx cpwvp mur mvvurdwbrd nkdru bpr mvvurdwbwko morkvt jx vpmubrurd vjhhrorl mkd nkwerulwbwrl wk bpr spwhwsswkrl. wb mhlj jxxrul lmlwv rdnvmbwjk sujoumyl bpujnop wbl jnkwju pwop lvpjjh mkd lrkwju pwop lvpjjh drsmubyrkbl. msmub xujy wbl ymkdmbr jx wklbunvbwjk, bpr nkwerulwbt suwdrl wbl rabrklwer rkomoryrkb wk urlrmuvp mkd rabrklwjk bpmb lrkrxwb bpr mvmdrywv…

An online store website is looking to upgrade their systems and practices: stronger encryption for customer information, b) a system for detecting when unauthorized users are trying to access their site, and c) a way to train their staff on how to keep customer and company information more secure so they will not be a victim of cyberattack. Design a finite state machine to model the identification and authentication process when 2-Factor Authentication is used. Identify states and state transitions. Assume that inputs are valid or invalid usernames and valid or invalid authentication factors, and outputs are messages for the user. Make sure to include explanations.

Calculate the entropy of the following systems and order them according to increasing security Notice(I need branches d and e) (a) A 6 digit PIN code with exactly 5 different numbers (b) A 6 digit PIN code with exactly 4 different numbers (c) A 9 character password with lower- and upper-case letters and numbers, where all the numbers are at the end. (d) A passface scheme with four 5x5 grids and three 6x6 grids, each containing 1 face for recognition (e) A combination of the passface and DejaVu system with six 5x5 grids. On each of the first 3 grids there is 1 face to recognize and on each of the last 3 grids there are 2 faces to recognize

Please show explaintion for steps and the formulas used thank you.

Paragraph Styles 15011 2 3 I4 5 CH6 7 U BI9 10 11 12CE 4 15 16 17 1 18 cyber If Bob and Alice want to share the same session key Ks, please describe how the two use their private and public keys to distribute Ks

Suppose Alice has a public key generated from the primes 409 and 617 with exponent 29. She receives a message 105744 from Bob which was encrypted using this key. Decrypt the message.

Is it feasible to produce secret keys for use in cryptographic protocols on a desktop computer using software in such a safe way that they can be utilized, and is this something that is even achievable?