Prove that decryption in a Feistel cipher can be done by applying the encryption algorithm to the ciphertext, with the key schedule reversed.

(a) Let mini-DES represent a DES cipher with only three rounds. Assume the plaintext was P and ciphertext was C. The key K generated three round keys K1, K2, K3. (i) Draw the block diagram of the implementation of the encrvotion process of mini-DES. (ii) Write the equations to get the blocks for each round. (iii) Justify why DES is considered a Feistal cipher.

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…

Show all of the steps needed to encrypt and decrypt the ASCII message “YES” without a modular arithmetic calculator in an RSA cipher with public key (143, 7).

Consider the affine cipher f(p) = 3p+4 (mod 26), where p is the plaintext representation of the character under consideration. For example the plaintext of the letter A is 0, B is 1, C is 2, ... Z is 25. Use this cipher to encrypt the letters I, N, G, R (changing the numbers back to letters at the end.

The definition of a Shift Cipher can be expressed as follows:Def. Let x, y, k ∈ Z26 with the encryption operation as ek(x) ≡ x + k mod 26 and thedecryption operation as dk(y) ≡ y - k mod 26.Given the provided letter encoding, what would be the encoding of the plaintext word ATTACKafter applying a shift cipher with a k=17?

Cryptanalysis can be achieved through exhaustive key search for a Caesar Cipher. Explain how this would be accomplished.

Let k be the encipherment key for a Caesar cipher. The decipherment key is 26 – k.One of the characteristics of a public key cryptosystem is that the encipherment anddecipherment keys are different. Explain why the Caesar cipher is a secret keycryptosystem, not a public key cryptosystem?

Note: 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 = 4. The plaintext given by 01100101 —D ХоXјX2XҙX4X5X6X7 when encrypted by the LFSR produced the ciphertext 10010100 — Уo У1 У2 Уз Уз У5 У6 Ут- 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, Pi = 0, po = 1).

Let E'(T,X) be a tweakable block cipher that has already been keyed. Given plaintext P = P1 || P2 || ... || Pn (ie, P is an n-block plaintext). Ci = E'(i, Pi) for i=1..nsum = P1 xor P2 xor ... xor Pntag = E'(0,sum) For simplicity let's say that E'(T,X) = ROTL(X,T+1)  (ie, X rotated left T+1 bits. If the block cipher block size is 8 bits and you are encrypting the two byte plaintext 67 89, what ciphertext and tag would be created? Fill in each box as a two-digit hex value. C1____? C2____? tag____?