Closure under prefix operator. Prefix operator is defined as: prefix(w E E*) = {w1 .. wk| 0< k < |w|}. For example, if a string w = asu, prefix(w) = {e,a, as, asu}. Show Prefix(L) = {prefix(w)| w E L} is a CFL if L is context-free.

Suppose that a security specialist and a remote command team are using the RSA cryptosystem to send a message. The command team selects p = 17 and q = 11. Assume e is chosen to be 3. What is the value of Ø?

How does secret key cryptography really work in practice? What is it exactly? Please provide a short explanation in your contribution, e.g., how it has previously operated. Do you have any opinions on how it is currently performing?

Plain text values, P(1)=10, P(2)=18,P(3)=27 p=23, q=29 Select a value of E thats not relatively prime to following b = (23-1)(29-1) = 616. Encrypt and decrypt all the values using RSA encryption. What issues do you encounter? What leads you to think why this happens?

The following is a message encrypted using keyword cipher and you know the keyword is CYBERSECURITY and the key letter is “a”. Decrypt the message and show all your work. OIR GJN OTG KJM OCH OCO OTO PER OIC OBC HYR SJM GRE TNO ICO JSE RNT MRO JUJ JHF RCM H

I'm perplexed by the idea of two-factor authentication. To what degree does it contribute to password security?

How can we tell if one method of authentication is safer than another?

They are a small, close-knit family of his. Do you think you could give a brief explanation of each?

Encrypt the message DEFEND using the RSA system with n = 43*59 and e = 13.  First translate each letter into an integer and group together pairs of integers, so you have three 4-digit numbers (padding 0’s in the front if necessary).  Work with each of these numbers to encrypt them.  The ciphertext should also be three 4-digit numbers.

The following is a message encrypted using affine cipher and you know the multiplicative key is 7 and the additive key is 3. Decrypt the message and show all your work. RFS DEY DCL CFA XXV HDE YFO REV WVO VEX VHD EYF ORE VAD BQO BOW EYD WVF ORF XVK XLP YBO BEL QDB XEV WDH BOW EYF OTF ORA DBQ OFO ROB ELQ BAA NQD XLA EX