Zodiac Killer Ciphers – Let's have a Look at Unicity Distances With Excel

#cryptology, #cryptography, #cryptanalysis

In this video, I have a look at the unicity distances of the Z-408 and Z-340 ciphers. The unicity distance is the minimum amount of ciphertext needed for cryptanalysis to have only one valid possible solution, when deciphering the ciphertext. Ciphertexts with lenghts below the unicity distance have with very high probability multiple "valid" solutions, meaning, solutions that can not be distinguished to the real valid solution (= original plaintext).

The Z-408 is encrypted using a pure homophonic substitution cipher. The Z-340 is encrypted using a homophonic substitution cipher and an additional "layer" of transposition cipher. For both, I try to compute the unicity distance using Excel.

You can find David Oranchak's newest Zodiac Killer cipher video, which I also mention in my video, here: https://www.youtube.com/watch?v=UfrFSrI05hk

The equation I used for computing the keyspace size of the homophonic substitution cipher you can find here: http://www.cs.sjsu.edu/faculty/stamp/RUA/homophonic.pdf

Video about unicity distance: https://www.youtube.com/watch?v=cxJcTyhzepI

Videou about columnar transposition ciphers: https://www.youtube.com/watch?v=4ONnQonBeZA

Video about Z-408 cipher (homophonic substitution cipher): https://www.youtube.com/watch?v=wVwSn_7q0Cc

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 Zodiac Killer Ciphers – Let's have a Look at Unicity Distances With Excel канала Cryptography for Everybody