BTW, for those of you who like to analyze the strenghts and weaknesses of the modified Vigenere cipher. The modifications introduce one major flaw which can result in the encrypted text not being decrypted correctly. Special recognition to the person who can name and explain this weakness.

However, this flaw will not affect the examples provided in this challenge and you are not required to code around this flaw.
_________________________
There are two types of vessels, submarines and targets.