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Jess M.
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This Questions on Cryptography 3 questions in the file here

Customer Question

this Questions on Cryptography 3 questions in the file
here is the link for the file
Submitted: 10 months ago.
Category: Software
Expert:  George Sibiya replied 10 months ago.


Welcome to JustAnswer.

How soon do yo need it?



Customer: replied 10 months ago.
Thank you for responding, 3 days from now
Expert:  George Sibiya replied 10 months ago.

Ok cool. I'ill work on it over the weekend.

Customer: replied 10 months ago.

Just checking. How is the assignment going so far?

Expert:  George Sibiya replied 10 months ago.

I am still on it but seeing that its taking longer than I anticipated I'll keep it open for other experts by opting out while doing it.

Customer: replied 10 months ago.
No problem it's still due until tomorrow
Expert:  Bruce Wilner replied 10 months ago.

More Google nonsense. Could you possible paste the questions into the Messages stream? Or is everyone in such a rush to have Google pirate the entirety of their content?

Customer: replied 10 months ago.

1- Compare the security and performance advantages and disadvantages of each variant of CBC mode: a fixed IV, a counter IV, a random IV, and a nonce-generated IV.

2- Suppose you, as an attacker, observe the following 32-byte ciphertext C1 (in hex)

4D 11 30 28 13 C7 8C EB 31 21 20 B0 70 B4 C3 B4
FA 3A 20 12 02 13 1C FD C5 44 07 25 D3 96 1F 74

and the following 32-byte ciphertext C2 (also in hex)

50 15 30 30 56 E6 91 BF 22 6E 22 B0 7D E0 CB B5
F0 6E 3A 22 15 0D 19 E5 8A 40 1A 31 D1 8D 03 74

Suppose you know these ciphertexts were generated using CTR mode with the same nonce. You also know that the plaintext P1 corresponding to C1 is

49 6C 69 6B 65 49 6E 74 72 6F 64 75 63 74 69 6F
6E 74 6F 43 72 79 70 74 6F 67 72 61 70 68 79 21

What information, if any, can you infer about the plaintext P2 corresponding to C2?

3- Let P1,P2 be a message that is two blocks long, and let P'1 be a message that is one block long. Let C0, C1, C2 be the encryption of P1, P2 using CBC mode with a random IV and a random key, and let C'0, C'1 be the encryption of P'1 using CBC mode with a random IV and the same key. Suppose an attacker knows P1, P2 and suppose the attacker intercepted and thus know C0, C1, C2 and C'0, C'1. Further suppose that, by random chance, C'1=C2. Show that the attacker can compute P'1

Customer: replied 10 months ago.
Relist: Inaccurate answer.