THINK ABOUT IT

$10\mathrm{.}1.$ Vigenere is a $q,$ cipher.

$10\mathrm{.}2$: While DES uses blocks of binary numbers transformed using a $64-$bit key, there are actually only $$ available to the actual key.

$10\mathrm{.}3.$ How many Feistel cipher rounds does DES perform?

$10\mathrm{.}4$: Euler's totient function returns:

$q,$ A public key half

$q,$ Key space from which a key can be chosen

$q,$ Positive integers less than $n$ that are relatively prime to $n$

$q,$ Large factors of prime numbers

$10\mathrm{.}5$: DESIECB:

$q,$ Uses $128$ bits for a key to process each block of data

$q,$ Uses $64$ bits at a time and each block of data

$$ Uses two keys, one to encrypt and the other to decrypt

$q,$ Is the strongest of encryption modes for DES