My Fantastic Contraptions

Posted on October 3, 2008 by Jeff Fitzsimons

A collection of solutions for Fantastic Contraption:

My Solutions:

  • Tube – a minimal tube crawler.
  • U-Turn – a floppy, crawling chariot.
  • U-Turn (again)) – a simple cart which uses leverage to apply force on the ceiling.
  • Back and Forth – an awful contraption.
  • Back and Forth – a better version which uses many wheels for low friction, and no bridge.
  • Higher – a ridiculously simple stick-flicker.
  • Around the Bend – a tiny triangle that flops to change direction.

Solutions by Others Which I Like:

My Experiments:

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Neat Flash Games for Nerds

Posted on October 1, 2008 by Jeff Fitzsimons

These three games present interesting logic puzzles:

  • Fantastic Contraption – build a machine to get an item into the target zone.
  • Light-bot – provide simple commands to make your robot traverse obstacles (publisher site with annoying, talking banner ads is here).
  • Chronotron – solve puzzles using a time machine.

    Fantastic Contraption

    Light-bot

    Chronotron

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A Good Orthopedist in San Francisco

Posted on September 18, 2008 by Jeff Fitzsimons

I needed to see someone about my shoulder/neck injury. On the recommendation of a coworker, I went to see Dr. Jon Dickinson. He seems to be very nice, knowledgeable, and happily explains what he’s observing, rather than just writing a prescription.

Contact Information

Dickinson, Jon A, MD
California Pacific Ortho and Sports Med
3838 California St Rm 715
San Francisco, CA 94118
(415) 668-8010

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Color Test

Posted on September 16, 2008 by Jeff Fitzsimons

I just took a fun test to determine how good I am at discriminating colors. Lower values are better. My results:

  • Your score: 8
  • Gender: Male
  • Age range: 30-39
  • Best score for your gender and age range: 0
  • Highest score for your gender and age range: 1464

Neat! Take the test here.

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Stripping an Authenticode Signature

Posted on September 12, 2008 by Jeff Fitzsimons

We needed to modify the resources of an installer and then apply an Authenticode signature. Unfortunately, it already had a signature on it, and modifying the resources of an executable with a signature results in a corrupted signature. The Microsoft signing tools cannot recover from this situation, so:

It is not possible to re-sign a file after modifying its resources.

However, it is possible to remove the existing signature, modify the binary, and then apply a new signature. There are two approaches (which almost certainly amount to the same thing):

  1. Use delcert.exe from the this XDA Forum post (note, this is not the same as the SMS Server 2003 tool ccmdelcert.exe, which deletes all SMS certificates on a machine).
  2. Write an application which calls ImageRemoveCertificate.
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Using Certificates and Signtool

Posted on September 12, 2008 by Jeff Fitzsimons

Obtain a Software Publisher Certificate

Your Certificate Authority will supply one of the following:

  1. a Personal Information Exchange (.pfx) file
  2. a Software Publisher Certificate (.spc), and a Private Key (.pvk) file
  3. a CER-encoded X.509 Certificate (.cer), and a Private Key (.pvk) file

For the second and third case, these file must be converted to a Personal Information Exchange (.pfx), using the Pvk2Pfx.exe tool.

Convert SPC or CER to Personal Information Exchange (.pfx)

Syntax for .spc conversion:

pvk2pfx -pvk filename.pvk -pi password -spc filename.spc -pfx output.pfx

The syntax is identical for .cer conversion:

pvk2pfx -pvk filename.pvk -pi password -spc filename.cer -pfx output.pfx

Sign the Executable

Signtool.exe can be used to sign executables (.exe) and Dynamic Link Libraries (.DLL).

Basic Signature

signtool.exe sign /v /f filename.pvk /p password executable

Signature With Timestamp

signtool.exe sign /v /f filename.pvk /p password /t timeurl executable

Where timeurl is the URL of your Certificate Authority’s timestamp server (e.g. http://timestamp.verisign.com/scripts/timestamp.dll for VeriSign)

Signature Verification

signtool verify /pa executable

/pa indicates that the “Default Authenticode” verification policy is used. Omitting the switch will cause the verification to fail, which does not necessarily mean that a given file isn’t Authenticode signed.

Resources

Posted in Cryptography, Technology | 1 Comment

PE Format

Posted on September 12, 2008 by Jeff Fitzsimons

While investigating Authenticode, I become curious about the Portable Executable format. This is the file format used by all Windows executables.

Here is a good overview in the context of .Net. And here is the referenced image which is missing from that post (originally http://jfmasmtuts.blowsearch.ws/Ch2/peheader2.jpg):

Windows PE Header Format

This missing image turns out to be part of a fantastic overview of the PE architecture. While the original article appears to be long gone, it lives on in an archive (and as a PDF in my own archive).

Here is a significantly more dry introduction, from MSDN.

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mssign32.dll

Posted on September 11, 2008 by Jeff Fitzsimons

With CAPICOM deprecated, MSDN suggests using the mssign32.dll functions. There are two fundamental problems with this:

  1. No example code whatsoever is provided.
  2. No header file is provided.

Well, at least I can do something about #2. Here is a minimal version of a header file for mssign32.dll. It includes direct function declarations, as well as function pointer typedefs.

The function pointers can be used with LoadLibrary/GetProcAddress to dynamically call the functions, as in:

SignerSignPtr pSignerSign = 
    (SignerSignPtr)GetProcAddress(hModule, "SignerSign");
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Make MSDN Website Load Faster

Posted on August 28, 2008 by Jeff Fitzsimons

The MSDN website sucks. It loads extremely slowly, and is visually cluttered.

It turns out that MSDN has a low-bandwidth (“loband”) option. This will cause MSDN to render using much simpler HTML, which loads much more quickly and has a very clean appearance. To use this feature, tack “(loband)” at the end of the URL, before the .aspx suffix.

For example, here are the MSDN pages for SendMessage:

Note that you can make this the default rendering method by clicking on “Persist low bandwidth view” at the top of the page:

Persist Low-Bandwidth View

(source)

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Photographer’s Rights

Posted on August 15, 2008 by Jeff Fitzsimons

The Bert P. Krages website has a handy, downloadable PDF version of the “The Photographer’s Right”.

If you object to the recent harassment of photographers in public places, I suggest that you download this, print it out, and carry it in your camera bag.

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