# Questions tagged [hill-cipher]

The Hill cipher is a historic polygraphic substitution cipher invented by Lester S. Hill in 1929.

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### Hill cipher, unknown letter value

I've been struggling on this problem for a while now : the Hill cipher is well-known to be vulnerable to known-plaintext attack due to its linearity. Given a key matrix $K$ of size $n\times n$, one ...
• 151
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### Hill Cipher known plaintext attack

I know a plaintext - ciphertext couple of length 6 for a hill cipher where its key is a [3x3] matrix. Based on what I've read and learned, to attack and crack keys of [n x n], if we know a plaintext -...
• 141
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### An unbreakable Hill cipher?

Why don't we use a Hill cipher of 100 × 100? Or even bigger? That would be close to unbreakable. The number of possible keys in a 2 × 2 Hill cipher is 157248. For 100 × 100 the number is beyond limits....
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### Problem while decrypting Hill cipher

I have a plaintext "monday" and ciphertext "IKTIWM" and $m=2$. I want to find the key of the Hill cipher. I made a matrix  \begin{bmatrix} a_1 & a_2 \\ a_3 & a_4 \end{bmatrix}\begin{...
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### Hill cipher concepts

I have some questions about the Hill cipher. There is a rule for key K: Determinant of matrix and number of characters of the alphabet must be coprime. What does ...
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Key space is the set of all possible keys that can be used to generate a key. We using the number of valid key to describe it. I've given a hill cipher of block size $k$ over alphabet of size $p$, ...