Let's Program a Hash Preimage Searcher to Break Passwords

#cryptology, #cryptography, #cryptanalysis

This is the first video of a new series on our YouTube channel. I call this series the "Let's program crypto!" series. In the series, I show how to implement cryptographic applications in .net C#. In this first videos, I show how to implement a password breaker (preimage searcher), that searches for passwords (preimages) of cryptographic hash functions. So you can try to program this by yourself in C# (or use the shown ideas with another programming language).

In fact, we will program a "HashPreImageSearcher" program (as a console application) in C# from the scratch, that searches for a pre-image (e.g. a password) of a hash value of arbitrary hash functions (which are implemented in the cryptography namespace of the .net framework). With this searcher, we will be able to define the pre-image alphabet, meaning, which characters (A-Z,a-z,0-9, etc) our preimages may contain. The searcher also shows the current progress, the search speed (hashes/preimages per second), and the estimated time left for the search.

With SHA-1 (on my video capture PC) we are able to search about 500,000 hash values/preimages per second. With SHA-256, we are able to search with a speed of about 1,000,000 hash values/preimages per second. And this with only 1 CPU core. Multi-threading is not part of this video - but will be implemented maybe in a later video.

I explain in detail the ideas behind the implemented search algorithm. For example, I will show how to walk over every possible word of a defined length that can be created using the given alphabet.

Before you watch the video and when you have no knowledge of hash functions, you should first watch my introduction to hash functions (https://www.youtube.com/watch?v=Rwvpngxp438) and passwords (https://www.youtube.com/watch?v=637UDE9MrlQ&t=4s).

I also made a video about the installation of Visual Studio, tortoiseSVN, etc. You probably need the installation of Visual Studio. So have a look at https://www.youtube.com/watch?v=YaSd_4t19nk&t=3s

You may download Visual Studio 2019 Community Edition here: Visual Studio 2019 Community Edition : https://visualstudio.microsoft.com/vs/

If you are interested in learning the basics of cryptology, you should also have a look at our video series about basics of cryptology – also for beginners: https://youtu.be/jbumW7Ym03o

You may download the latest version of CrypTool 2 from here: https://www.cryptool.org/en/ct2/downloads

Видео Let's Program a Hash Preimage Searcher to Break Passwords канала Cryptography for Everybody