How to uncover keys from using double encryption schemes such as Hill and Vernam Cipher

Kelvin Li

8/17/24, 1:47 PM

I have a quick question. How would you decrypt an encryption scheme, involving both Hill and Vernam Cipher. The order of encryption is Hill Cipher then Vernam Cipher. Problem is that only final cipher text and the original plain text is intercepted. Without the cipher text derived from the Hill Cipher, I can't think of any idea of decrypt it or did I miss something crucial here.

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hill-cipher

fgrieu

8/17/24, 2:37 PM

It's unclear what the Vernam cipher is when applied to ciphertext of the Hill cipher. The Vernam cipher usually is bitwise XOR with a constant, or a rolling set of constants. But usually and unless otherwise specified, the Hill cipher's character set has size 26, with no natural conversion to binary, and at least 32 characters in the output for character-per-character encryption. Are the ciphers more precisely defined? Or at least, what seems to be the ciphertext character set ? Is it feasible to try all keys for either cipher, and check if there's a matchign key for the other?

DannyNiu

8/18/24, 5:37 AM

"did I miss something crucial here" - Meet-in-the-Middle?

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: How to uncover keys from using double encryption schemes such as Hill and Vernam Cipher

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