sábado, 26 de setembro de 2009

A Stick Figure Guide to the Advanced Encryption Standard (AES)

via Moserware by Jeff Moser on 9/26/09

(A play in 4 acts. Please feel free to exit along with the stage character that best represents you. Take intermissions as you see fit. Click on the stage if you have a hard time seeing it. If you get bored, you can jump to the code. Most importantly, enjoy the show!)

Act 1: Once Upon a Time...

introsadaes act 1 scene 03 cinderellaaes act 1 scene 04 startedaes act 1 scene 05 judgeaes act 1 scene 06 nbs decreeaes act 1 scene 07 luciferaes act 1 scene 08 anoint desaes act 1 scene 09 des ruledaes act 1 scene 10 des defeatedaes act 1 scene 11 triple desaes act 1 scene 12 nist decreeaes act 1 scene 13 ralliedaes act 1 scene 14 rijndaelaes act 1 scene 15 voteaes act 1 scene 16 wonaes act 1 scene 17 intelaes act 1 scene 18 crypto question

Act 2: Crypto Basics

aes act 2 scene 01 three big ideasaes act 2 scene 02 confusionaes act 2 scene 03 diffusionaes act 2 scene 04 key secrecyaes act 2 scene 05 aes details question

Act 3: Details

aes act 3 scene 01 sign thisaes act 3 scene 02 agreementaes act 3 scene 03 state matrixaes act 3 scene 04 initial roundaes act 3 scene 05 xor tributeaes act 3 scene 06 key expansion part 1aes act 3 scene 07 key expansion part 2aaes act 3 scene 08 key expansion part 2baes act 3 scene 09 key expansion part 3aes act 3 scene 10 intermediate round startaes act 3 scene 11 substitute bytesaes act 3 scene 12 shift rowsaes act 3 scene 13 mix columnsaes act 3 scene 14 add round keyaes act 3 scene 15 final roundaes act 3 scene 16 more rounds the merrieraes act 3 scene 17 tradeoffsaes act 3 scene 18 security marginaes act 3 scene 19 in picturesaes act 3 scene 20 decryptingaes act 3 scene 21 modesaes act 3 scene 22 questions what really happensaes act 3 scene 23 math

Act 4: Math!

aes act 4 scene 01 algebra classaes act 4 scene 02 reviewing the basicsaes act 4 scene 03 algebra coefficientsaes act 4 scene 04 remember multiplication growthaes act 4 scene 05 cant go biggeraes act 4 scene 06 clock mathaes act 4 scene 07 clock math polynomialsaes act 4 scene 08 divide by mxaes act 4 scene 09 logarithmsaes act 4 scene 10 using logarithmsaes act 4 scene 11 polynomial as byteaes act 4 scene 12 byte operationsaes act 4 scene 13 byte inversesaes act 4 scene 14 sbox mathaes act 4 scene 15 round constantsaes act 4 scene 16 mix columns mathaes act 4 scene 17 crib sheetaes act 4 scene 18 got it nowaes act 4 scene 19 so much moreaes act 4 scene 20 gotta goaes act 4 scene 21 the end


I created a heavily-commented AES/Rijndael implementation to go along with this post and put it on GitHub. In keeping with the Foot-Shooting Prevention Agreement, it shouldn't be used for production code, but it should be helpful in seeing exactly where all the numbers came from in this play. Several resources were useful in creating this:

Please leave a comment if you notice something that can be better explained.

Update #1: Several scenes were updated to fix some errors mentioned in the comments.
Update #2: By request, I've created a slide show presentation of this play in both PowerPoint and PDFformats. I've licensed them under the Creative Commons Attribution License so that you can use them as you see fit. If you're teaching a class, consider giving extra credit to any student giving a worthy interpretive dance rendition in accordance with the Foot-Shooting Prevention Agreement.

Things you can do from here:

Freddie Exec Compensation, Bandos, Market and more

via Calculated Risk by CalculatedRisk on 9/25/09

Michelle at Footnoted.org digs up the employment contract for Freddie Mac's new CFO: Taxpayer funded signing bonus at Freddie Mac?
• annual compensation of $3.5 million (this includes $675K in salary, $1.6 million in something called “additional annual salary” and $1.1 million in a target incentive
• a $1.95 million signing bonus
• immediate buyout of Kari’s house
Why is Freddie paying more than the private sector? And I bet Geithner is jealous about the house deal!

Stock Market CrashesClick on graph for larger image in new window.

This graph is from Doug Short of dshort.com(financial planner): "Four Bad Bears".

Note that the Great Depression crash is based on the DOW; the three others are for the S&P 500.

And the Bandos are moving on up in Miami! From nbcphiladelphia.com: After Miami's Ritzy Bubble Bursts, Squatters Move on Up
Miami's squatter problem has garnered national media attention over the past year and a half, as the foreclosure crisis threatened to transform the Magic City into something resembling a lawless, "Mad Max"-esque landscape.

The squatters mostly kept a low profile, moving in ... to neighborhoods where they could take over unnoticed.

But now come reports that squatters are seeking out more ritzy neighborhoods, including the pricey, tree-lined streets of Coral Gables.
A check of county records found that the home went into foreclosure over a year ago, just about the time residents said the alleged squatters showed up.

The bank which owns the property hired a realtor to sell it last month ...
Maybe the lenders should sell the foreclosed homes?

And from the LA Times: Calls to renew home buyer tax credit get louder in Washington. Yeah, an expensive, poorly targeted tax credit for those not suffering during the recession. This isn't as dumb as allowing the FHA DAP to continue (Downpayment Assistance Program - the poster child for bad housing policy), but close. Why not a "first-time renters" tax credit for anyone who hasn't rented for 3 years? That makes as much economic sense.

Things you can do from here:

Upload MP3 To YouTube with Mp32Tube

Upload MP3 To YouTube with Mp32Tube: "

If you have tried uploading your MP3 files to YouTube, then you might know that YouTube does not support this feature. If you want to upload any MP3 file, then it needs to be converted to video format before uploading. Mp32Tube is a free service which allows you to upload MP3 files to YouTube through its interface. You don’t have to convert to any video format, only upload the MP3 file through Mp32Tube.


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Mp32Tube settings

Mp32Tube is a free service for uploading MP3 files with a background to YouTube. Mp32Tube plans to have a premium paid account with more features.

Mp32Tube Home Page


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