Bob receives an encrypted message from Alice:

$-$hikv

First he applies the encoding function

$C$:$\{-,a,b,c,$dots,$z\}\{0,1,2,3,$dots$26\},C(-)=0,C(a)=1,$dots,$C(z)=26.$

and obtains this sequence of integers:

Bob decrypts the message using the decryption function

$D$:$\{0,1,2,3,$dots$26\}\{0,1,2,3,$dots$26\}D(x)=(7*(x-2))mod27.$

He gets the sequence of integers:

Applying the inverse of the encoding function $C$ Bob obtains the plain text: