Hint 1: The final message ends without padding, but it looks very "alphanumeric." If it contains lowercase, uppercase, and numbers, what is the most common 64-bit encoding?
View Hint : Hints 2
Hint 2: If you see a string of all caps and the numbers 2-7, you’ve likely stumbled into Base32.
View Hint : Hints 3
Hint 3: The flag format is HackCTF{...}. If your decoded text looks like UnpxPGS{...}, you might need to "rotate" your thinking by 13 places.