Cryptography

Martian message part 2

We got the following message

I think that's the key "fselkladfklklakl" 

KDERE2UNX1W1H96GYQNUSQT1KPGB

If we look at the type of encryption/cipher that has an output as full string of letters.

After trying a few i found that it is a VIGENERE CIPHER.

Using this website we can decipher the text.

http://www.dcode.fr/vigenere-cipher

The flag is FLAGU2JNU1R1X96VOFNKHLB1GEWQ