How Does SHA-256 Work?

learnmeabitcoin · 374.6K views · 2020-05-12 · 22:59

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Overview

A step-by-step animated explanation of how SHA-256 works, from padding and message schedule to the compression function and final hash, with source code for the animations.

On Hacker News

Commenters call it clear enough to implement the algorithm from, and teachers use it in courses.

Recommended by 3 HN people across 3 months · HN mentions 2020–2022

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What people said

7373737373 · 2022-03 · Strong recommendation
I found this video to be an excellent explanation and sufficient to implement the algorithm: [VIDEO] Code: [LINK] This site contains a nice visualization: [LINK]
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oconnor663 · 2022-02 · Recommendation
Oh this is great. When we taught SHA-256 last semester, we linked to this YouTube video: [VIDEO] . Next time we do it, we'll probably link to both. Having several different ways to visualize the same thing is very helpful, and I like that this one moves quickly. A couple of details missing from this visualization are how you pad a message to be a multiple of the block size, and how you chain blocks together to form a longer message. In the pseudocode at [LINK] , that's the "Pre-processing (Padding)" part and the "for each chunk" loop just below it. I get why you'd want to leave those things out, since they're not really the interesting part, and the screen is already pretty packed as it is. If anyone's feeling curious about implementing this yourself, take a look at these project notes: [LINK] . At some point I'll clean that up for public consumption, but for now just ignore the parts about grades and cheating :)
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1_player · 2020-05 · Recommendation
Here's the author doing an in-depth explanation of how SHA-256 works using this code: [VIDEO] I'm halfway through, but looks very well done, thanks!
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Sources

Video by learnmeabitcoin, played through YouTube.

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