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Division: Div C – High School

Event Rules: See the National Rule Manual

National Event Page: Here


Teams will cryptanalyze and decode encrypted messages using cryptanalysis techniques for historical and modern advanced ciphers. 


Teams must bring writing utensils and may bring up to three stand alone non graphing non programmable non scientific 4 function or 5 function calculators.  No resource materials may be used.  The Event Leader will provide scratch paper and will include a resource sheet with the Morse Code Table, English/Spanish letter frequencies, Porta Table, and Baconian mappings as needed for the questions on the exam.


High score wins.


This event allows up to 3 team members.  Teams are allowed to divide and conquer the test.

Event Resources:

User guide for Codebusters – 45 pages of resources!
Online Interactive tests instructional video
Codebusters 2019 Coaches Clinic Presentation (2018 Rules)
Codebusters Test Tools
The State event supervisor for Codebusters has set up a twitter handle to send out tips and tricks.  @NCSO_cb
Important update from the Coaches institute.  The K2 alphabet hint is actually a K1 alphabet hint.  Everything described works the same, just the label is a K1 instead of K2.  You can read on how to solve with a K1 alphabet at
Previous tests can be found at
CIA – break the code
The Imitation Game
Test Builder Demo

Make your own codes:

Hill Cipher
Affine Cipher
   Encode/Decode Tool:
Vigenere Cipher
   Encode/Decode Tool:

The STEM Yard podcast featuring an interview and Q&A with Event Leader John Toebes.