No one on Earth knows how to reverse one of the most popular computer algorithms. Yet it's really easy to compute oneway. You could make billions of dollars if you solved this mathematics problem, which is computed quintillions of times per second in the race for mining Bitcoin. SHA256 has some amazing properties, is useful for digital signatures, cryptography, authentication, and is a central part of the Bitcoin protocol.

(**** UPDATE 2021: After two years, I've finally posted a followup video, an introduction to Bitcoin. You can find it here:    • Intro to Bitcoin  Is it the most dis...   )

Bitcoin and other "cryptocurrencies" rely on oneway hash functions like the SHA256 algorithm to secure the blockchain where all the transactions are kept.

In this video, I explain some of the bigpicture ideas behind this one function. Other cryptocurrencies use similar ideas.

Comments, suggestions, or errors? Let me know in the comments, and I'll fix them in an upcoming followup video.

Take a look at some of my other videos:    • Matthew Weathers Teaching  

Links
Wikipedia about SHA256:
https://en.wikipedia.org/wiki/SHA2'>https://en.wikipedia.org/wiki/SHA2

Current Bitcoin difficulty:
https://www.coinwarz.com/difficultyc...

Big number calculator:
https://defuse.ca/bignumbercalculat...

Credits
BitCoin & Money Photo:
Copy Link to Credit: (CCBY 4.0) Cryprocurrency360.com
https://www.flickr.com/photos/bitcoin...

Bitcoin mining farm:
(CCBY 2.0) Marko Ahtisaari https://www.flickr.com/photos/moia/

Fourier Transform Graph:
(CCBY 4.0) Jake
http://pgfplots.net/tikz/examples/aut...

Wikipedia Hash Function Algorithm illustrations:
https://en.wikipedia.org/wiki/SHA2'>https://en.wikipedia.org/wiki/SHA2
(CCBYSA)