Decipher the Message [Forum game]

I'm not a big fan of the math in the first message

HELLO.
WE'RE THE ALSAN.
WE'RE A REBEL.
DO NOT PASS TO THE STATE OR ELSE YMU WILL DIE.
WE NEED YMUR HELP.
DECODE THIS.

I assume "YMU" and "YMUR" are supposed to be you and your, but I have no clue what ALSAN means.