Iam using an Affine Cipher that uses a product cipher to encrypt a message. I know the 2 functions/key.
$fa(x) = 3x + 5$ $mod(26)$
$fb(x) = 5x + 7$ $mod(26)$
I need to find the products of these functions. I am familiar with multiplying two functions.
$ ab(x) = fa(x) * f(b) $
PROBLEM
However, I have never multiple two functions with a particular modulus before. Can I ignore the modulus as they are both the same?
So thus it will be $ab(x) = (3x + 5) * (5x + 7) = 15x^2 + 46x + 35$
Then I will add the modulus 26, making it :
$15x^2 + 46x + 35$ $mod(26) $