Question

The encrypted version of a message is LJMKG MGMXF QEXMW. If it was encrypted using the affine cipher what was the original message?

Short answer

$f^{-1}\left(p\right)=15(p-10)mod26$ the original message

Step-by-step solution

Step 1

Given encryption function:

$f\left(p\right)=(7p+10)mod26$

Step 2

Since$7^{\ast }15mod26=105mod26=1,\text{th}$, the corresponding decryption function is:

$f^{-1}\left(p\right)=15(p-10)mod26$