Below is the cipher text I am trying to break and as you can see its rather short which is why I am having so much trouble.
WOYFN ZCMSH VUVTG BFUTW ABTZP FHIMF TFOSU UXFQC HKVKG MPUUQ MHRXI OVBRZ EPJYF KKVJW GEIOV HUKEB JUNSM THIMF TFKUB ULMMQX
What I know about this ciphertext:
- Key is 6 characters long and repeats (Given by the person who encrypted it)
- There is a single character missing from the start of the ciphertext! (Also given)
- It uses a simple cipher I believe a vigenere cipher.
- Friedman IC: 1.143 (kappa-plaintext: 0.4396) which is why i think its a vigenere cipher
I have spent many hours on this but to be honest im not very good at breaking these codes.
My problem that iv run into is that once I break the cipher into its sections they are all very short and hence frequency alaysis fails.
I would really appreciate if someone could either confirm or find the crypto system being used as well as any more information about how one would find the plaintext + key or better yet find the key itself and explain how you manage it with such a short piece of ciphertext
Edit: There was some debate as to the validity of this question so here is some more information from my attempts:
- ?ZUUZFUKUXZKEKSFU IC = 3.6833 (kappa-plaintext: 1.4167)
- WCVTPTXVUIEKIEMTL IC = 1.1471 (kappa-plaintext: 0.4412)
- OMTWFFFKQOPVOBTFM IC = 2.1029 (kappa-plaintext: 0.8088)
- YSGAHOQGMVJJVJHKM IC = 1.3382 (kappa-plaintext: 0.5147)
- FHBBISCMHBYWHUIUQ IC = 1.5294 (kappa-plaintext: 0.5882)
- NVFTMUHPRRFGUNMBX IC = 0.9559 (kappa-plaintext: 0.3676)
These numbers don't look good. they are almost all drastically off normal distribution for any language.
The main point to my question is:
- Does Vigenere Seem like a reasonable fit (given those streams are correct)?
- Is it possible to use that analysis in any way? I cant see how it can be effective with only 17 characters per stream. Most letters frequencies are 0.
- What other ciphers are possible? How could I identify that they are in use?
I am happy to provide more information I am just not sure what else is useful.