Saturday, July 21, 2012

Password Management

The Problem:

  • Using the same password on multiple websites is known to be insecure.
  • Creating and remembering a different password for every website is difficult.


My solution requires remembering two pieces of information:
  1. A single secure key.
  2. A simple string hashing function.
When registering for a website, generate your password by applying your hashing function to the domain name of the website (ignoring the top level domain) and append the output of that to your secure key. VoilĂ , you now only need to remember O(1) bits of information instead of O(N) to register N websites.


Step 1: generate and remember a single secure key. Let's say my key is now "0vDga5"
Step 2: generate and remember a string hashing function. Here is an example of a function to create a three character hash:
  • Character 1: The first letter of the string.
  • Character 2: The length of the string.
  • Character 3: The last letter of the string.
Now when registering an account on the following websites, my password would be: 0vDga5g5l 0vDga5i4b 0vDga5a1a 0vDga5d6n

Thursday, July 19, 2012

Lossy Video Compression

Using a three dimensional DCT I can drop components from both the temporal and spatial dimensions. Here is what dropping high frequency temporal components looks like:

Sunday, July 15, 2012

Lossy Audio Compression

Here is an experiment I ran performing lossy audio compression with DCT:


Audio Spectrogram

Using FFTW I made a program to visualize audio spectrograms. The song "Windowlicker" contains an image hidden in its spectrogram - here is the output from my program:

Discrete Cosine Transform

Today I spent a few hours playing with discrete cosine transforms using the FFTW library. I have been experimenting using DCT for lossy compression in different domains. Here is a visualization I made of lossy image compression using an increasing number of frequency components: