“Why encrypting twice with two symmetric keys using the same algorithm doesn’t give you twice the security?” was the question that was asked in a recent CSE509 (System Security) class. I had the intuition that encrypting with the same algorithm twice with two different keys, K1 and K2, is essentially equivalent to encrypting with one key (say, K3). However, I didn’t know how to convince others about this.

Someone pointed out that, since Symmetric Cryptography is essentially a combination of Permutation and Substitution at a very basic level (the person was referring to P-Boxes and S-Boxes, found in many algorithms), doing it twice is essentially equivalent to doing it once with some other key.

I found that this was a more convincing argument (though very informal), about the security of the proposed mechanism.

I wanted something that would dump a binary file on the terminal in hex. Turns out there is a tool called hexdump!

hexdump filename

Voila!

Face it, giving talks seems like a performing art to some extent. Making sure you retain everybody’s attention throughout the talk, is easier said than done. Last semester Professor Bender gave us some tips on how to give an awesome talk without having the charisma of <Insert-your-favorite-heartthrob’s-name-here/>.

Deepak has very carefully jotted down some of the tips in his blog post.