8 bits only: What is Cryptography?

What are keys?

I mean, surely you’ve used a key before!? We all lock our doors when we leave our house or car, and we sure don’t leave our mailbox open all the time, so why would we treat our data any different?

  • Without publicizing encryption schemes, it is much harder to form standardized mechanisms for encryption atop existing protocols.
  • Publicizing encryption schemes leads to significantly more peer-reviewing of the algorithms, and in turn, increased robustness.
  • If exposed, it is much easier to replace a key, than an entire encryption scheme.
  • Even with best efforts, it is difficult to keep an entire encryption scheme secret, compared to just a key.
Credit: Intro. to Modern Cryptography, Katz

What is a cryptographic key?

We can drill down the definition of a key in modern cryptography as follows:

It’s not that simple, right?

Ok, I have left this definition intentionally vague, after all how else am I going to entice you to read the follow up post!? There are a lot of open-ended questions at this point from my definition of a key, and some of the ones you may be having are:

  • Is the same key used for encrypting and decrypting a message?
  • How do we initially share the keys that we use to encrypt the messages on a channel, over that very same channel? Is this even possible?
  • Do we use the same keys for encryption of channels with many different parties?



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Aashray Anand

Aashray Anand

Working on storage management and infrastructure at Azure SQL