I'm trying to work through an encryption assignment and the instructions aren't particularly clear because they don't go hand in hand with the lecture video.
Using encryption key e = 9 in modulo 23, perform the following calculations:
- Take the secret message M = 21, encrypt this message as a number E. Note down the value of E.
- Let d be the decryption key for this encryption system. Compute d. Complete the following sentence: e × d ≡ a(mod b). Note down the value of a, b and d.
- Use the results above (or an alternative approach) to decrypt the secret message M that was encrypted as E = 15. Note down the value of M.
I was sorta able to do the first one but I have my doubts. So e = 9, p = 23(got this from a classmate) and M = 21. The encryption algorithm given in the lecture was E ≡ M^e (mod p) and that turned out to be 17. So the message 21 was encrypted to 17. I am going off of p = 23 from a classmate but I don't quite get she got that value from.
The 2nd issue that I'm having is E = 15 in #2. The value is suppose to be 17.
The 3rd issue I'm having is the value of a. I know the value for e and I can find d by isolating it but I don't know what to make of a.
I'm not asking anyone to do my homework for me. My problem is that this is super unclear and half-assed. I was wondering if those well-versed in encryption can break this down for me and highlight my mistakes.