Question $1[13$ pts$]$

Answer the following short$-$answer questions:

$$ Which of the following is not the principal goal of the cryptography? Select among Confidentiality, Integrity, Availability

$$ Which of the following is the principal goal of encryption? Select among Confidentiality, Integrity, Availability

$$ What is a cipher?

$$ How many keys are used in a secure communication between two parties that use a symmetric$-$key encryption algorithm?

$$ What might be the size of an encrypted message, if the size of the plain text $15$ bits. You can choose more than one. Select among $14$ bit, $15$ bits, $16$ bits

Question $2[10$ pts$]$

Any encryption operation uses a cipher and a key. Explain the Caesar cipher and the possible keys used by giving an example.

Question $3[12$ pts$]$

Describe the terms permutation, substitution, and the mode of operation. Provide examples to these terms in the context of the Vigenere Cipher.