Entry to CIA Part #1

As I searched for different topics on Google, my whole screen suddenly went black and gave me this letter:

Dear Reader, if you have come across this message, you may be applicable for the CIA. We are looking for some of the best mathematicians in the world. We think you might be one. To confirm your skills, we require that you decode this message: 30 265 75 5 340 . (d) (e) 135 40 (d) (e) = (t) 220 (e). Only the best mathematicians are able to decode this. If you can solve it, write back to us, and we will proceed with the next steps.

NOTE: The period and equals sign are included in the final message; they don't have anything to do with the decoding.

Hint 1:

Divide all numbers by something that they are all divisible by.

Hint 2 (use after 1):

Use PT to change the numbers into one letter or two letters.

Hint 3 (use after 2):

Combine all the letters to form one string!

NOTE: The back story is fictional.

Next Part: Part #2.

• Not that it matters, but wouldn't this be more of a CIA thing than a Secret Service thing? CIA are the code breakers. Secret Service are mostly just the protection detail for high level officials. Jun 1, 2022 at 16:56
• @DarrelHoffman You're probably right! I didn't think much about that. I can change it!
– user80078
Jun 1, 2022 at 17:06

This cipher (despite the CIA's claims) actually has little to do with mathematics, and much more to do with...

chemistry.

First:

Divide each number by 5, the common divisor of all numbers in the ciphertext:

6 53 15 1 68 . d e 27 8 d e = t 44 e

That's the mathematics part over with. Then:

Replace each number with the Periodic Table symbol that corresponds to these atomic numbers:

C I P H Er . d e Co O d e = t Ru e

The result is:

programming-like syntax saying CIPHEr.deCoOde = tRue, implying that the cipher has been successfully decoded (or is that 'decooded'?! After all, it seems there is an extra 'O' in the plaintext output...).

• Nice job! That's correct.
– user80078
Jun 1, 2022 at 15:33