- Don’t forget the Module 4 Assessment is on Friday. Calculators allowed like last time. Details about the material (and review problems) are on the “Goals” page on the navbar above.
- To Do: An Elliptic Curve El Gamal Ciphertext Chain! Today’s question: what did 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 = [3,11655832467975276266127,1] 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 6 or fewer letters. Translate this to an integer and add three 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 #ciphertexts 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.