Search the Internet and learn about the Data Encryption Standard $($DES$).$

Then, based on the RSA and DES answer the following questions:

a$)$ What is the purpose of padding in cryptography algorithms such as DES? Explain it using

a simple example $[6$ marks$].$

b$)$ We know that the size of the key in DES is $64$ bits, assume for padding we just add $0$ at

the end of the plaintext $($the original message$),$ what is the result of padding for the

following text? At first replace the $$YYY$$ with the first $3$ letters of your name or family

then calculate the padding $($show the result in hexadecimal format$)$:

$$YYYComputerSecurity$$

Show your answer step by step $[6$ marks$].$

c$)$ We know that RSA works with numbers. Assume we want to encrypt the plaintext

M$=$ComputerSecurity$.$ We know we should use the following formula: C$=$Me mod N in

which $($e$,$N$)$ is the public key. But before using this formula, at first, we should convert M

into a number. To do so$,$ there are different solutions. Search the Internet and explain one

of them. Show different steps of the selected solution on the given plaintext

M$=$ComputerSecurity$$ as an example. Consider padding as well $[10$ marks$].$

d$)$ What is a digital signature? Is it possible to generate a digital signature using RSA? What

about DES? Explain your reasoning $[6$ marks$].$