This messaging system was established in 1973 for secret communication with a Soviet diplomat, Aleksandr Ogorodnik, who was spying for the CIA. He was given the code name TRIGON, which this coding system was named after. The secret message was concealed behind a postage stamp and mailed to the agent.

Post-Gazette message:

29906 53763 59397 51498 16933 47714 74639 86231

26381 99433 54373 99163 26888 03500 74649 60682

Decoder:

24765 93659 55146 09380 18882 67898 69598 95436

25341 88038 31282 39057 21708 51305 66499 20567

• Step one: Copy the numbers in the Post-Gazette message onto a piece of paper, leaving approximately one inch between lines.

• Step two: Copy the numbers from the decoder directly beneath each digit from the message.

• Step three: Subtract the decoder numbers from the Post-Gazette digits using "non-carrying" math.

To get you started here is how to set up the first four sets of numbers:

29906 53763 59397 51498 .....(message)

24765 93659 55146 09380 .....(decoder)

05231 60114 04251 52118 .....(deciphered)

• Step four: Separate the deciphered message into two-digit numbers and convert each couplet into letters; A-Z are numbered 01 to 26. For example, the first letter deciphered with the first couplet 05 would be E.

If you decipher the code, send in your message to participate in a random drawing for a $25 gas card. Either e-mail the answer to magazine@post-gazette.com with SPYCODE in the subject line. Or snail mail your answer to Kathy SaeNgian, Pittsburgh Post-Gazette, 34 Blvd. of the Allies, Pittsburgh, PA 15222. Must be postmarked by Saturday, June 28. In both cases, please include your name, address and daytime phone.