For Friday:
 Please look over your exams and the solutions and let me know if there are any grading questions etc. There’ll be a redo opportunity as before (more info soon).
 Look at the solutions to the previous Daily Post if needed.
 Quantum Key Distribution!

 I think this will get confusing with everyone simultaneously on the #ciphertexts channel, so I want you to do this in pairs in the “QKD pairs” channel category of discord. There you will find plenty of text channels, so fill them up with two people each as you arrive, taking the first empty spot (the first person needing a partner or the first unused channel). Announce your arrival. The first person to arrive in a channel is Alice, the second person to arrive is Bob. Once two people are there, it’s full, so pick the next channel. You’ll do all communication on the channel so I can help you debug if it doesn’t work.
 Open up the QKD BB84 Tools. The first box contains some code to initialize; no need to read this, just run it. The second box is a spot where you can either create photons (in our instantiation, they are just mysterious looking integers), or measure existing photons. It just holds an example for now.
 Once you know if you are Alice or Bob, follow the protocol for your role.
 If playing the role of ALICE:

 Here’s a spreadsheet you might find useful (optional; view only but you can copy it).
 Choose a sequence of 16 random choices of basis: example V L V V etc. The best way to do this is with a random number generator (like randint() in Sage).
 Now choose a sequence of 16 bits: example 011001010101 etc. Again, true or good pseudorandomness is best.
 Use your two sequences to generate photons using the command create_photon in the QKD BB84 Tools page. This will create 16 integers (the photons), which you should obtain and paste into the channel as your “outgoing photon stream”.
 Wait until Bob harvests your photon stream and reports that they are done “measuring” the photons.
 Then, post to the channel the list of bases you used on your photons.
 Bob will also post their list of bases used on the channel.
 Then, determine the shared secret key from these two lists. Share it and see if Bob agrees.

 If playing the role of BOB:

 Here’s a spreadsheet you might find useful (optional; view only but you can copy it).
 Choose a sequence of 16 random choices of basis: example V L V V etc. The best way to do this is with a random number generator (like randint() in Sage). Keep this secret for now.
 Alice will create a stream of photons (integers). Harvest (cutnpaste) Alice’s photon stream, and use the command measure_photon() in the QKD BB84 Tools page to measure them using your list of bases (first basis to measure first photon etc.) Record the measurements and keep them secret.
 Report to the channel you have finished measuring.
 Then, report to the channel your list of bases.
 When Alice also reports her list of bases, derive the shared secret.
 Then, post the shared secret you derived to check if it agrees with Alice’s.

 To Do: When you’re done, just post to canvas a screenshot or record of your experience; you can screenshot the channel or you can screenshot your spreadsheet or a text file you kept a record in; whatever, just to show you did it.
