Comparing cypher block chaining to cypher feedback mode in terms of the number of encryption operations necessary to transport a large file, cypher block chaining is more efficient than cypher feedback mode. Which one is more efficient, and how much more so?

Comparing cipher block chaining with cipher feedback mode in terms of the number of encryption operations necessary to transport a large file reveals some interesting differences.Which of these methods is more effective, and by what percentage?

In modern encryption, plaintext is encoded in binary form. Each bit in a bit stream is encrypted into its matching ciphertext, while bits in a block stream are grouped together to create groups of bits prior to encryption.

Encrypting with TDEA and a single key is pointless, because it is equivalent to encrypting with the original "single" DES, which is no longer considered strong enough to resist feasible attacks. In your own words (do not quote in any way from any source), briefly explain why decrypting with TDEA and a single key was a useful operation when TDEA was developed.

Each of the following is a true/false statement about a tweakable block cipher (TBC). Place a checkmark next to each true statement. In the questions mentioning E', let E' be a random instance of a TBC and E'(T,X) be the result of using E' with tweak T and input X. Group of answer choices: (1)For TBC security both the current key and tweak in use must be kept secret from adversaries. (2)Each time a new tweak is given to a TBC, the TBC behaves like a new random permutation. (3)When a TBC is used once per tweak its outputs may be considered (4)A TBC is a prominent part of the design of OCB. (5)If X1 ≠ X2, then always E'(T,X1) ≠ E'(T,X2) (6)If T1 ≠ T2, then always E'(T1,X) ≠ E'(T2,X)