Write a program in Python or C++ that has TWO functions:

Function One is called: _encrypt
Function Two is called: _decrypt
Function one takes plain text, and assesses the indexed value of each letter in the string. For example, a=1, b=2. It then adds three to the indexed value, and produces encrypted text, based off of the plain text.
Function two reverses this.
Here is sample output:
_encrypt('how do you do')
Unsecured: howdoyoudo
Secured: lsahscsyhs
_decrypt('lsahscsyhs')
Unsecured: lsahscsyhs
Secured: howdoyoudo