Here is the full list of all 21 Room 40 achievements.
Completed secret message #1
Completed secret message #2
Completed secret message #3
Completed secret message #4
Completed secret message #5
Completed secret message #6
Completed secret message #7
Completed secret message #8
Completed secret message #9
Completed secret message #10
Completed secret message #11
Completed secret message #12
Completed secret message #13
Completed secret message #14
Completed secret message #15
Completed secret message #16
Completed secret message #17
Completed secret message #18
Completed secret message #19
Completed secret message #20
Completed all ciphers!