The fun session!

Today’s topic, “Transaction security in an online world.” This is one of the main reasons I agreed to “teach” this class, because the math is fun. Well, to me. :)

For example, previously I noted here that I like to use humor. Today on the screen as the “students” arrived was a quote (origin unknown) — “There are only 10 types of people in the world: those who understand binary and those who don’t.”
(“10” is the binary representation of the number “2” in the decimal-based number system.)

I talked about “clock arithmetic,” a card trick, prime numbers, Pierre de Fermat (1601–1665), RSA encryption, and showed the “students” several examples of encrypting and decrypting an increasingly large number (i.e., like a 16-digit credit card number).

The image above of course has to do with the card trick: eight perfect shuffles (“out-shuffles”) restores a 52-card deck of cards to its original order. Of course I prepared a spreadsheet and this post shows the progression through eight perfect shuffles. » Faro shuffle (American) :: weave shuffle (British) :: dovetail shuffle

Posting this more than a year after the fact, I now see something I hadn’t noticed before:     the 10♥ and 6♦ swap positions with every shuffle.
Huh. They are the 18th card from the top and the 18th card from the bottom. Huh. 🤔

Also: Compare Shuffle 3 above to a recent post.

So I apologize: another screenshot post for keeping my 365 project as a photo- or image-journal. But this “class” is what is occupying me these days. Not much time for photography.

Bitcoin: Money or “Novelty”?
    » Session 1: “Money”: Definitions; “types” of money; a brief history
    » Session 2: Cash, digital transactions and tracing transfers
    » Session 3: Transaction security in an online world
    » Session 4: Bitcoin and “blockchains”: Motivations, design, & problems
    » Session 5: Cryptocurrency wrap-up: Conclusions? Q&A

[ Screenshot _20220331 :: ]

Looking back
  1 year ago: “Travel day 1 [Filler]”
2 years ago: No post
3 years ago: No post
4 years ago: “The Great Vigil of Easter”
5 years ago: “Lamp”
6 years ago: “From death to new life”
7 years ago: “Another row on the lake”
8 years ago: “Antirrhinum majus”
9 years ago: “What a difference a day makes!”
10 years ago: “Creature in my office!”
11 years ago: “Purple!”

31st March 2022 31st Mar 22