This is a write up on challenges 12 and 14 of the cryptopals cryptography challenges.

It’s been a couple years since I started working on the cryptopals project. But, two years later, I am returning to this project hopefully to finish it all the way through. Given the time that has elapsed since I started cryptopals in earnest, I thought it would be a good idea to go back through […]

First off, if you’ve ever visited my site before, I just want to take a moment to thank you for visiting, and for your readership. There was a time a couple years ago where I would post to this blog monthly. I obviously haven’t written on this blog for a couple years. There is a […]

In 2006, Daniel Bleichenbacher shared a discovery in an evening session at a cryptography conference: Several implementations of RSA-based PKCS 1 v 1.5 cryptographic signature verification were fatally flawed and susceptible to signature forgery. It is as bad as it sounds. The sad part: The flaw in the signature verification algorithm is that the signature […]

I just finished cryptopals challenge 39, in which I had to implement RSA. For me, it wasn’t enough for me to just implement the RSA algorithm. I sort of needed to understand a bit about the underlying number theory. I say that because I’ve faced instances in the past where a typo or error in […]

Secure Remote Password (SRP) is a protocol by which a user in a system is able to log in to that system without the system ever knowing or storing the user’s password. Consider this description of the SRP protocol from cryptopals challenge 36: Replace A and B with C and S (client & server) C […]

What if the server that verified MACs took longer to verify a correct mac than an incorrect one? Or, perhaps put differently, what if you could tell the difference between a more correct guess than an obviously wrong one? If you can, you can break MAC authentication schemes, and that’s what the cryptopals authors are […]

Continuing my series on the cryptopals challenges… In section four, two of the challenges require you to get past a checksum test by spoofing a hash associated with a forged message. The idea is that if you can manage to pass a query string to an application (say a web application) that has been toyed […]

The subject of today’s post is breaking counter mode encryption, which directly concerns three cryptopals challenges: challenge 19, challenge 20, and challenge 25. (And maybe more … I’m only as far as challenge 25 at this point.) What is counter mode encryption? Counter mode encryption is a method of encryption in which the content of […]

As was said in my last post, I’m doing cryptopals. Just last night I finished Challenge 23. I was able to successfully clone a 32-bit Mersenne Twister pseudorandom number generator (PRNG) from its output. You can see how I did this by checking out my solution in my github repo. If you’re like me when […]