Problem 2606. Decrypt the cypher using XOR encryption (for beginners)

Inspired by Project Euler n°59

Each character on a computer is assigned a unique code and the preferred standard is ASCII (American Standard Code for Information Interchange). For example, uppercase A = 65, asterisk (*) = 42, and lowercase k = 107. A basic encryption method is to take a text file or a sentence, convert the bytes to ASCII, then XOR each byte with a given value, taken from a secret key. The advantage with the XOR function is that using the same encryption key on the cipher text, restores the plain text; for example, 65 XOR 42 = 107, then 107 XOR 42 = 65.

Your task has been made easy, as the encryption key consists only of a upper case character (different in every tests). You must know that the original text contains common FRENCH words about MATLAB.

Decrypt the message and find the sum of the ASCII values in the original text.