For Friday, October 13th, 2023

  1. Friday we are beginning some new stuff, but here’s something fun we didn’t get to do before the test: an RSA signature chain!
      1. Look up RSA signature in the lecture notes, or Monday’s video, if you need a refresher.
      2. Decide on an answer to the question “my new year’s resolution is…” which fits in 6 characters.  This is your “document” you will sign.  (I won’t hold you to it!)
      3. Look up your old public/private RSA key pair.  If you lost it, you’ll have to break your own public key to recover your private key!  (Or make a new one and replace your old one from the #public-keys channel).
      4. Turn your document into a number using text-to-integer.
      5. Sign your document (as an integer).  Post your document (as text, not integer), public key, and signature together on the #ciphertexts channel (For example, My document is ….. , my public key is A=…., and my signature is s=….).
      6. Find someone else’s signed document and verify it, then announce whether you succeeded.  If you didn’t succeed, seek help from me or them to debug the situation.
  2. Now, warmup for Friday’s class:  consider the polynomials $f(x) = 3x^2 + 2x$ and $g(x) = 3x + 1$, where the coefficients of these polynomials live modulo $5$.  What is:
      1. f(x) + g(x)?  remember to treat the coefficients mod 5.
      2. f(x)*g(x)?
      3. the remainder of f(x) divided by g(x)?  if it isn’t clear what I mean by this, what should I mean by this?