It’s a write-up about the challenge : Ringzer0CTF - Martian Message part 2
Challenge 63 - Martian Message part 2
1. Challenge
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I think that's the key "fselkladfklklakl"
KDERE2UNX1W1H96GYQNUSQT1KPGB
2. Solution
It is a vigenere cipher. Simply shift the ciphertext by the key. We used this website to decode the Martian message. https://www.dcode.fr/vigenere-cipher
The flag is : FLAGU2JNU1R1X96VOFNKHLB1GEWQ