- To Know: Reminder that there was a mistake on the Module 3 Assessment and because of the mistake I gave everyone until Wednesday. It had to do with Problem 4; if you did it already and want to re-do it, you can resubmit just that problem on canvas, or resubmit everything. It shows previous and current submissions. Please be clear, whatever you do.
- To Know: There was also a typo on the last problem of the ReDo problems for Modules 1 and 2; this has also been updated on canvas, and I’ve set the deadline back until Monday. Phew!
- My apologies for both of those errors.
- To Do: An Elliptic Curve El Gamal Ciphertext Chain! Today’s question: what do you miss during the pandemic? You will encrypt your answer. Here are the steps:
- Keep notes as you do all this.
- Here are the EC El Gamal Tools you can use to do this.
- As a group, we will all use the elliptic curve E given by y^2 = x^3 + x^2 + x + 1 over the finite field of p = 123456789101234567891027
elements. Note that p is 3 mod 4. We will furthermore use the point P = [3,11655832467975276266127] on E, which has order 61728394550949287614731.
- You should create a private and public key pair based on the information given above. Publish your public key on the #ciphertexts channel on discord. Keep your private key in a text document somewhere to use for decrypting later.
- You should answer the question (What do you miss during the pandemic?) with a word of 7 or fewer letters. Translate this into ASCII, and add two digits of “padding” as explained in class.
- Turn your message into a point on the elliptic curve as described in class.
- You should then obtain the most recent public key on the channel, and encrypt your ASCII message (turned into a point on the curve) to that public key. Post your encryption to the channel, mentioning the owner of the public key it is encrypted to.
- You should then keep an eye on the channel and when someone encrypts a message to your public key (they should mention you), you should decrypt it and announce what that person misses during the pandemic, mentioning them.
- When someone decrypts your message, you should give them a thumbs up to let them know it’s right (or let them know if it isn’t).
- Hand in your notes from this exercise to the canvas dropbox.