You're a secret agent working for the NSA and you have monitored the messages between two friends for a while now. Suddenly, their messages become encrypted and you're on high alert. The first part of their message was sent twice (accidentally), an encrypted and decrypted version. This was the message:
The package has arrived, I am ready for pickup. When and where shall we meet?
Further analysis show the keyword was
password. The next part of the message was sent encrypted, but with a different key. All you could find out about the keyword was that it is 4 letters long. The message was this:
Time is running out and you fear it may be dangerous! Can you decrypt the message in time?
EDIT: I will post a hint later on today
C++ code (very basic) here for algorithm (won't spoil the answer!)
(This is my repo) https://github.com/Cube777/cube-lib/blob/master/src/cube-encrypter.cpp
Hint 2: Another hint:
The keyword is not an English word, but a sequence of 4 letters (not an abbreviation but a popular sequence of 4 letters)