Rolling your own crypto: Everything you need to build AES from scratch

Post by watwut » Wed, Jul 13, 2022, 9:00 AM UTC

traceroute66 wrote: post #18

stingraycharles wrote: post #14

Earlier quoted context omitted.

It’s absolutely worth it to roll your own crypto if you want to learn from it. I feel like there is almost a stigma against articles like these because we’ve all been conditioned so much to avoid even thinking about it lol. I did some deep dive into AES and RSA at some point in a distant past, it was a learning experience that to this day allows me to make much better decisions when choosing algorithms.

> It’s absolutely worth it to roll your own crypto if you want to learn from it No. If you want to "learn from it", the first thing you should do is buy a copy of Bruce Schneier's Applied Cryptography . Just reading (and fully understanding !) that book will alone put you in a position where you already know more about cryptography than 90% of other people. If after that you still want to play around with rolling you…

Post by traceroute66 » Wed, Jul 13, 2022, 9:19 AM UTC

watwut wrote: post #22

traceroute66 wrote: post #18

Earlier quoted context omitted.

> It’s absolutely worth it to roll your own crypto if you want to learn from it No. If you want to "learn from it", the first thing you should do is buy a copy of Bruce Schneier's Applied Cryptography . Just reading (and fully understanding !) that book will alone put you in a position where you already know more about cryptography than 90% of other people. If after that you still want to play around with rolling you…

Just no. This idea that people are not allowed to learn by doing things and must read huge books first is absurd. The guidelines for learning you gave here are impractical for majority of people who are interested. It is actually good when people are trying to learn about security. Just about worst thing these absurd rules achieve is that effectively only rule breakers are allowed in.

Post by charlieyu1 » Wed, Jul 13, 2022, 9:54 AM UTC

badsectoracula wrote: post #19

Mordisquitos wrote: post #6

Earlier quoted context omitted.

> you shouldn't use your (or their) self-made cryptography in production Absolutely, and that was the very first thing I thought when I saw the title. For some reason I've got the "don't roll your own crypto" commandment heavily ingrained into my brain (even though I've never been in any context where I might have tried), together with "don't let the frying pan handle stick out over the edge of the cooker in case a k…

I always found this "mantra" shortsighted and damaging on the long run - if nobody does their own crypto then who does their crypto? You are incentivizing people against learning this by that and a very significant part of learning something is actually using it in practice.

Post by [deleted] » Wed, Jul 13, 2022, 10:16 AM UTC

charlieyu1 wrote: post #27

nullc wrote: post #2

It's much more interesting to implement AES without the table lookups-- as doing so requires constructing a boolean circuit that computes the same result as the tables, more useful too since the table lookups result in security killing side channels. :) The author might be surprised at how often someone's random "learn 2 crypto" ends up in use in production. Kudos for the warnings, though I doubt that actually accomp…

Isn't table lookup constant time?

Post by Grimburger » Wed, Jul 13, 2022, 10:17 AM UTC