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

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...

Act 2: Crypto Basics

Act 3: Details

Act 4: Math!

Epilogue

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:

• The Design of Rijndael is the book on the subject, written by the Rijndael creators. It was helpful in understanding specifics, especially the math (although some parts were beyond me). It's also where I got the math notation and graphical representation in the left and right corners of the scenes describing the layers (SubBytes, ShiftRows, MixColumns, andAddRoundKey).
• The FIPS-197 specification formally defines AES and provides a good overview.
• The Puzzle Palace, especially chapter 9, was helpful while creating Act 1. For more on how the NSA modified DES, see this.
• More on Intel's (and now AMD) inclusion of native AES instructions can be found here and in detail here.
• Other helpful resources include Wikipedia, Sam Trenholme's AES math series, and this animation.

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:

• Subscribe to Moserware using Google Reader

Freddie Exec Compensation, Bandos, Market and more

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!

Click 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:

• Subscribe to Calculated Risk using Google Reader
• Get started using Google Reader to easily keep up with all your favorite sites

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.

With Mp32Tube, you can select any MP3 file and then use an image as background. The background can be uploaded from your PC and it needs to be in .JPG format. You can upload the MP3 either to Mp32Tube’s account or to your account. If you want to upload to your account, you need to authenticate with your YouTube account.

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

"