Salt vs Long Password

Salt is not as secure as long Password because salt is saved on server.

The problem short passwords face without salt is this: With access to rainbow table (kind of password-hash map), and the hash of password, a table look up returns the plain password, which is either your password, or a password the computer thinks is yours (collision).

Longer password requires a bigger rainbow table, and is therefore safer. However, people don’t like long password, and that is when salt comes into play. The server says to the user, “I will add some letters to your password but I will remember the added part so that you don’t have to”. The added part is the $SALT. Now we don’t have to remember the whole long password, at the cost that $SALT is no secret, because it’s saved by the server.

Here is a command I tried on my Ubuntu. As seen from this line in /etc/shadow, which is for password ‘mypass’: $6$3zTDsuzi$00giYxlM8HUtmuH3qBC0J0IgDzOg8hKzUZZwjb.3lKRWvtwTikVECguVpaO3b.CGpNQYCc5EnRVEsDudt1eOU1      Salt is 3zTDsuzi, and algorithm is sha-512.  This command: $python -c ‘import crypt; print crypt.crypt(“mypass”, “$6$3zTDsuzi$”)’ returns: $6$3zTDsuzi$00giYxlM8…, which matches the line in shadow file.


Optic Fiber Network

I just put together an optic fiber network.
The components used:

  1. Switch: TRENDnet TEG-30284 4x10G SFP+ Slots, $300 on Amazon
  2. NIC: Intel Ethernet Server Adapter X520-2 about $150
  3. Cable: 10Gb Multimode Duplex OFNP Fiber from Cable Matters $10 On Amazon. Each cable needs two modules.
  4. Transceiver module: SFP+, 10GBASE-SR, MMF, 850nm, from 10Gtek, $20 on Amazon

The installation was smooth as long as the cable, module and switch match.


Green Screen Replacement

Our most recent project is green screen replacement.
The screen needs to be treated as green regardless of dark green or light green, and regardless of the brightness of the lighting, e.g. indoors or outdoors.
I used the HSV color space. A narrow threshhold was set on Hue component, with a wider threshold on Saturation, for what kind of green, and Value, for the lighting.
Here is my intuitive way of viewing HSV, which is not accurate, but worked in this project:
We make color by mixing paint with water, and shining light on it. Hue is the color of the paint, Saturation is how much paint to mix, Value is how much light to shine.