# How does hill cipher key exchange takes place?

I am giving a presentation in my college where hill cipher is a part of the presentation. I just wanted to know, how is the hill cipher key matrix is exchanged securely in order to decrypt the message?

• You should be aware that the Hill cipher is unsafe for messages sizably larger than the key. – fgrieu Aug 17 '18 at 6:04
• @fgrieu how so? – Srijan Singh Aug 17 '18 at 6:25
• A guess of the plaintext the size of the key allows to find the key by solving a linear system of equations. That guess can be verified by deciphering later ciphertext and checking if it makes sense. That allows to break the Hill cipher much faster than trying all keys. Also, the usual 3x3 variant only has $2^{44.3\ldots}$ keys, making it vulnerable to brute force key search. – fgrieu Aug 17 '18 at 8:18