Reply To: !

[the_cryptographer_formerly_known_as_madness]

Hi,

If anyone is having trouble with #113625, it may be because the description of the cipher is backwards. The shifts were applied BEFORE the hill cipher. What is likely to have happened is that an intern hit the “DECRYPT” button by mistake when generating the ciphertext. I.e., this is what happened:

plaintext → Vigenère cipher (keylength 3) → Hill cipher (3×3) → ciphertext

To decrypt:

ciphertext → inverse Hill cipher → inverse Vigenère cipher → plaintext

Due to the fact that the modulus, 28, has many small factors, the effect of the shift can sometimes be wiped out by the Hill cipher. So it might /look/ like parts of it were encrypted the right way round.

So, @upsidedown, before I attempt #113626, I would please like to see the code you used to generate its ciphertext.
Thank you for that, and for the challenges.