Every now and then, I read a question about learning how to break ciphers, or more generally how to become a cryptographer/cryptologist. From my vie

So, You Want to Learn to Break Ciphers

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2024-04-24 12:00:10

Every now and then, I read a question about learning how to break ciphers, or more generally how to become a cryptographer/cryptologist. From my viewpoint, the most important part of learning this skill is not advanced mathematics, but instead first learning how to think like a cryptographer. When you go to break a cipher, there are no instructions on how to do it. You simply need to get your hands dirty with the function under consideration and look for things that do not seem desirable for a secure function of that type. While having a bag of tricks is going to help, ultimately it’s your creativity, persistence, and skills that are more likely going to make the difference.

I believe that there are a number of hackers out there that already know how to think the right way, and it is simply a matter of exercising that thought process on some reasonable, non-contrived examples to begin to understand what it takes to be a cryptologist. You should not need to know advanced mathematics or advanced cryptographic techniques (such as linear or differential cryptanalysis) to get started. So welcome to my blog post, which provides a number of exercise for you to practice on. These examples mostly come from cryptanalysis that I have done, largely because I know the results, I was able to dig them up, and attacking them did not use advanced techniques. I am building a list of other examples at the bottom of this blog, and invite other readers to add to it.

I’m adding to existing resources because I thought I have a nice, small collection of my own that I have accumulated over the years. Like the Matasano challenges, my focus is on providing modern examples that are easy to break without complex mathematics or advanced cryptographic techniques. These examples illustrate how to think like a cryptographer without requiring all the complex background in the most advanced cryptanalytic techniques. If you can solve these problems (and your solutions may not necessarily be the same as mine), then you have the right type of thinking to become a cryptographer. This blog post is written for computer scientists without deep mathematics skills that want to learn how to do cryptanalysis, and teachers of cryptography for computer science students.