Suppose that Bob receives a PGP message from Alice. How does Bob know for sure that Alice created the message (rather than, say, Trudy)? Does PGP use a MAC for message integrity?

Alice encrypts a message using AES, and sends the ciphertext to Bob. Unfortunately, during the calculation of the third block, a lightning struck Alice’s house, corrupting the 2nd bit of the AES output (for the third block). Fortunately, nothing else of the calculation was affected. How much of the plaintext can Bob still recover if the mode of encryption is one of the followings: CBC, CFB, OFB, or CTR?

Imagine a Vigen'ere cypher encrypts a long string of text and repeats it in the ciphertext. Use this information to calculate the key's length.

Alice sets up an RSA public/private key, but instead of using two primes, she chooses three primes p, q, and r and she uses n=pqr as her RSA-style modulus. She chooses an encryption exponent e and calculates a decryption exponent d. Encryption and Decryption are defined: C ≡ me mod n and m ≡ Cd mod n where C is the ciphertext corresponding to the message m.  Decryption: de ≡ 1 mod φ(n) | Let p = 5, q = 7, r = 3, e = 11, and the decryption exponent d = -13. n = 105 & φ(n) = 48 Q: Alice upgrades to three primes that are each 200 digits long. How many digits does n have?

Remember that the TCP/IP protocol suite's transit phase is when packet rearranging and reassembly occur. A firewall can function at a lower abstraction level, such as the data layer or the Internet. If a traffic stream is out of order or erased, a stateful inspection firewall will be unable to learn anything about it.

Alice needs to transmit a 48-bit message using a 47-bit key. Suggest a scheme that is perfectly secure.

Bob's El Gamal prime number is p=907 and his secret key is a=16. Alice has encrypted x=13 for sending to Bob and her ciphertext is (37,♦). What is ♦ (mod p)? Select one: a. 512 b. 418 c. 253 d. 96 e. 419

Should a nonce be encrypted? O Yes, it prevents the message from being hacked. No, otherwise Bob (the receiver) couldn't read the nonce. O No, and you should never use a nonce in the first place. O Yes, otherwise Oscar (the enemy) would be able to intercept it.

Encrypt the messageWATCH YOUR STEPby translating the letters into numbers, applying the encryption function f(p) = (−7p+2), and then translatingthe numbers back into letters

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?