Animation of the AES algorithm

http://www.cs.bc.edu/~straubin/cs381-05/blockciphers/rijndael_ingles2004.swf

by wisesage5001 • 16 years ago

81 20 16 years ago

cs.bc.edu

verroq• 16 years ago

Shows how, but doesn't explain why, which make it completely pointless.

hartror• 16 years ago

The why would be useful but I would hardly say it is pointless. For example I understand the theories but I'm light on details given I have never implemented an encryption algorithm.

Hmmm weekend project?

djcapelis2• 16 years ago

Writing encryption algorithms as a weekend project should generally be approached in the same way as one might approach writing aircraft control code as a weekend project:

Never use it, never distribute it in a way that someone else might mistakenly think it's a good idea to use it (so posting it on github would probably be a mistake!) and expect your implementation to have bugs you don't realize. (Even if you shove plaintext in and get the right ciphertext out doesn't mean you've found all the bugs, it gets tricky and in some cases different specific algorithmically correct implementations can have not just different performance characteristics, but different runtime security characteristics.)

Otherwise, enjoy.

Most people tend to find weekend projects more fulfilling if they have a way to put them to use. So while I don't mean to go all "this is dark arts that no one should practice uninitiated" on you, I would encourage you to stifle your tendency to find a use for any encryption code you write that isn't peer reviewed. View it as purely an artform; code never to be utilized.

This is the same advice most security researchers give to themselves and others.

desigooner• 16 years ago

if you've worked with C++, there's a very well known and widely used library called Crypto++ that implements various encryption algorithms incl. AES. Give it a try.

uxp• 16 years ago

I've implemented complex encryption methods, but _only as coding exercises_, never ever ever as code that I would ever want to use outside of the exercise.

In your headers you should note that the code contained is for educational use only and is probably very flawed.

Please note: I'm not saying you're a terrible programmer and is guaranteed to botch this attempt. Encryption is a tricky beast. Best leave it to the maths geniuses.

Locke16892• 16 years ago

I'm pretty sure the number theory involved in the "why" is over most peoples' head.

gcb• 16 years ago

i agree that the why is complex. but threating it as "math is complex, so let's treat it as a religion and never question or try to understand. just accept." is just plain wrong.

So, the first step should be to NOT start with the "Advanced" standard :) look for block cyphers.

And if you found your self blocked on this little presentation during the non-sense (and not explained) column transformation step, this may help you:

http://docs.google.com/viewer?a=v&q=cache:H0QmIsUIBbkJ:w...

Understanding AES Mix-Columns Transformation Calculation Kit Choy Xintong University of Wollongong,

jeffreyg• 16 years ago

I disagree. They could add a lot of context by simply explaining the key and its importance, and the concepts of confusion and diffusion.

sid0• 16 years ago

No, not really. The most complex math AES uses is operations in the finite field GF(256). Given that addition in a power-of-2 finite field is simply XOR, I expect any good programmer to be able to get AES.

mfukar• 16 years ago

How is it pointless? Don't you find a visualization of abstract operations or code useful? How hypocritical.

Besides, the question 'Why does AES work the way it does?' is a completely different topic which should only be touched after the 'How does AES work?'.

moserware• 16 years ago

I explained more of the details and some of the "why's" in http://www.moserware.com/2009/09/stick-figure-guide-to-advan... , but most people seemed to stop reading before getting to them.

nitrogen2• 16 years ago

On step 4, AddRoundKey, shouldn't e5+17 be fc, not f2? Or is AES using something other than simple 8-bit modular arithmetic? It looks like the author did the arithmetic in his/her head, and accidentally used decimal for the second digit (5 + 7 = 12, mod 10 = 2).

dfreidin• 16 years ago

The + in a circle means xor, not plus

nitrogen2• 16 years ago

That's what I get for learning programming years before entering college. I forget standard mathematical notation, since I always use programming language operators (like ^) in my head. Further, I only checked the first row to make sure it was actual addition, and obviously 0xa0 + 0x04 == 0xa0 ^ 0x04.

I should've just checked here first (includes an image of the slide in question): http://stackoverflow.com/questions/839479/what-does-a-circle...

Aegean• 16 years ago

I am more interested in who did the animations. I need such animations to describe our software.

makmanalp• 16 years ago

Looks like ezabala at adinet dot com dot uy, Enrique Zabala. Universidad ORT, Montevideo, Uruguay

Animation of the AES algorithm

Related Stories