Tuesday, February 25, 2014

Trying to build gcc cilk from sources following the instructions at https://www.cilkplus.org/download. This step repeatedly fails since the gnu.org git server is slow or something:
git clone http://gcc.gnu.org/git/gcc.git cilkplus-gcc 

Here's how to incrementally do a giant git clone from a slow server.
git init
git add .
git remote add cilkplus-gcc http://gcc.gnu.org/git/gcc.git
git pull http://gcc.gnu.org/git/gcc.git
It's painful, but with enough git pull operations, I seem to be able to get everything. Thanks to http://superuser.com/questions/154647/how-to-continue-cloning-a-git-repository-that-the-download-was-stopped

Note: the git add . gave an error, but I don't know if that meant it was a no-op.

Thursday, October 17, 2013

I am general chair for Charles E. Leiserson's 60th-Birthday Symposium and Party. It's a symposium (for the techs) and it's a party (for everyone). Hope to see you there.

Monday, September 17, 2012

Thursday, May 31, 2012

How to digitally sign a pdf file using free software in GNU/Linux

I recently needed to sign a pdf document for legal purposes. The other party was willing to accept a digital signature. That does not mean copying an picture onto a pdf document. It's using public key crypto to sign the pdf document. Acrobat can do it, but I use free software, so, after about 30 minutes I figured out how to do it.

  1. I extracted my csail certificate from my browser. In firefox
    • edit->preferences->advanced->encryption->view certificates
    • select the certificate
    • then hit backup
    • save it as a pkcs12 file
    • you'll be asked for a password for the backup. You'll use this later.
  2. I got jsignpdf-1.3.0 and installed it
    • $ unzip JSignPdf-1.3.0.zip
    • $ cd jsignpdf-1.3.0
  3. I ran it: $ java -jar JSignPdf.jar
    • A simple window popped up with some forms to fill in.
      • keystore type: PKCS12
      • keystore file: choose the backup made of the certificate
      • keystore password: the password you used
      • input file: the pdf file to sign
      • output file: I chose another name to avoid overwriting something useful
      • I clicked the checkbox on "visible signature"
      • Went to the "settings" box next to 'visible signature"
      • I chose the page where the signature needed to be placed, and I chose coordinates. I found the coordinates by running gv input.pdf since ghostview shows the coordinates in the upper left corner. For example, I put my signature on page 7 and put signature at coordinates
        • 147
        • 482
        • 369
        • 519
      • I chose Display: "Signature name and decsription"
      • Hit "close"
    • Then "sign it" on the original jpdfsign window.

Monday, December 6, 2010

my webpages are mostly back

After being down for nearly a year my web content at bradley.csail.mit.edu is mostly back up at http://people.csail.mit.edu/bradley/.

There remain a few things missing...

Tuesday, November 30, 2010

MIT Academic Calendar

I created a google calendar for the MIT Academic Calendar. The calendar ID is gtfme9paltu2dfdac81f0p73us@group.calendar.google.com.

If you would like to volunteer to help maintain this calendar, please contact bradley@mit.edu. Originally I was using obpoblff7vffces4ot4g73b02g@group.calendar.google.com, but it's not being maintained, and I don't know how to contact the maintainers.

Monday, November 15, 2010


I've created planet supertech to aggregate supertech-related blogs.