$1.$ Describe the terms "plaintext," "ciphertext," and "secret key" as they apply to symmetric encryption. $(3$ marks$)$

$2.$ Cryptographic systems are characterized along three independent dimensions. What are these three dimensions? $(3$ marks$)$

$3.$ The term "strong encryption" refers to encryption schemes that make it impractical for unauthorized persons to gain access to plaintext that has been encrypted. What properties are characteristic of a strong encryption algorithm? $(3$ marks$)$

$4.$ Describe the differences between a monoalphabetic cipher and a polyalphabetic cipher. Is the Caesar cipher a polyalphabetic cipher? $(3$ marks$)$

$5.$ In one of his cases, Sherlock Holmes was confronted with the following message:

Znk yozagzout oy mxgbk$.$ lusk osskjogzkre

Although Watson was puzzled, Holmes was immediately able to deduce the type of cipher. Describe the cipher being used to encrypt this message. Can you decode the message? Is this cipher susceptible to brute$-$force cryptanalysis? $(3$ marks$)$

$6.$ Describe the difference between a block cipher and a stream cipher. What is a typical block$-$size used in a block cipher? $(3$ marks$)$

$7.$ What is the difference between diffusion and confusion? $(3$ marks$)$

$8.$ Describe three forms of attack on a public$-$key encryption scheme. $(3$ marks$)$

$9.$ Briefly describe the RSA cipher. $(3$ marks$)$

$10.$ If the prime numbers e$,$ p$,$ and q are $17,7,$ and $11,$ respectively, in the RSA technique, derive the public and private keys. $(3$ marks$)$

$11.$ In a public$-$key system using RSA, you intercept the ciphertext $\backslash ($ C$=29\backslash ),$ sent to a user whose public key is $\backslash ($ e$=7,$ n$=33\backslash ).$ What is the plaintext $\backslash ($ M $\backslash )?$ Be sure to show all your work. $(5$ marks$)$