Straddling Checkerboard Examples

VIC cipher walkthroughs and practice exercises

Basic encryption examples

Simple encryption using the VIC cipher configuration. H is in the top row (position 3), E is at position 0, L requires two digits (63), O is at position 8.

Key: ESTONIARBlanks: 2, 6
0123456789
-ES2TON6IAR
2BCDFGHJKLM
6PQUVWXYZ
PlaintextHELLO
→
Ciphertext350363638

VIC cipher history

The VIC cipher was one of the most complex hand ciphers ever used. It was employed by the Soviet spy Reino Häyhänen (codename VIKTOR, hence VIC) during the Cold War. The straddling checkerboard was the first layer of this sophisticated cipher system.

Historical Note

The VIC cipher remained unbroken by cryptanalysts and was only revealed when Häyhänen defected to the United States in 1957. The full cipher involved additional steps including:

  • Chain addition (Fibonacci-like sequences)
  • Disrupted transposition
  • Final digit manipulation

The straddling checkerboard provides excellent compression for messages because high-frequency letters (like E, T, A, O, N, R, I, S) are encoded with single digits, while less common letters require two digits. This makes the output shorter and harder to analyze statistically.

Practice exercises

easy

Decode: 350363638 using key ESTONIAR with blanks at 2,6

easy

Encode: CAT using key ESTONIAR with blanks at 2,6

medium

Decode: 15350 using key ESTONIAR with blanks at 2,6

hard

Create a straddling checkerboard with key AEROTICS and blanks at 3,7. What would HELLO encode to?

Learning the Straddling Checkerboard Cipher

The best way to understand the Straddling Checkerboard cipher is through hands-on practice with real examples. This page provides progressively challenging Straddling Checkerboard examples and exercises to help you master this variable-length substitution cipher.

Basic Straddling Checkerboard Concepts

Building the Straddling Checkerboard Grid

The standard VIC cipher Straddling Checkerboard configuration uses:

  • Key phrase: ESTONIAR (8 high-frequency letters)
  • Blank positions: 2 and 6

This creates a Straddling Checkerboard grid where:

  • Position 0: E, Position 1: S, Position 3: T, Position 4: O, Position 5: N, Position 7: I, Position 8: A, Position 9: R
  • Row 2 (starting with 2): B, C, D, F, G, H, J, K, L, M
  • Row 6 (starting with 6): P, Q, U, V, W, X, Y, Z, ., /

Reading the Straddling Checkerboard Grid

Understanding the Straddling Checkerboard cipher grid structure:

  • Single digits (0,1,3,4,5,7,8,9) decode directly from the top row
  • Two-digit codes starting with 2 use extended row 2
  • Two-digit codes starting with 6 use extended row 6

Learn more about grid-based ciphers and their structures.

Worked Straddling Checkerboard Examples

Example 1: Encoding "HELLO" with Straddling Checkerboard

Using the Straddling Checkerboard cipher to encode "HELLO":

LetterPositionCode
HRow 2, Column 525
ETop row, Position 00
LRow 2, Column 828
LRow 2, Column 828
OTop row, Position 44

Straddling Checkerboard Result: HELLO → 2502828284 (or 25 0 28 28 4 with spaces)

This Straddling Checkerboard example demonstrates variable-length encoding: E and O become single digits, while H and L become two-digit codes.

Example 2: Decoding "183279" with Straddling Checkerboard

This Straddling Checkerboard decoding example shows the parsing process:

Parse the Straddling Checkerboard ciphertext from left to right:

  1. "1" → S (top row)
  2. "8" → A (top row)
  3. "3" → T (top row)
  4. "27" → wait, check "2" first - it's a blank indicator!
  5. "27" → G (row 2, column 7)
  6. "9" → R (top row)

Initial Result: 183279 → SATGR? Let's reconsider the Straddling Checkerboard parsing...

Actually: 1-8-32-79 or 1-8-3-27-9?

  • 1 → S
  • 8 → A
  • 32 → F (extended row 2, column 2)
  • 7 → I (top row)
  • 9 → R

Correct Straddling Checkerboard Decoding: SAFIR

This example shows why careful parsing is crucial in Straddling Checkerboard decoding. Use our Straddling Checkerboard decoder for automatic parsing.

The VIC Cipher Connection with Straddling Checkerboard

The Straddling Checkerboard cipher was the first step in the famous VIC cipher used by Soviet spies. The complete VIC cipher system involved these additional steps beyond the Straddling Checkerboard:

  1. Straddling Checkerboard - Convert text to numbers using the checkerboard grid
  2. Chain Addition - Add sequences using Fibonacci-like rules
  3. Transposition Cipher - Rearrange the digits in a disrupted pattern
  4. Final Manipulation - Additional modifications for security

The VIC cipher was considered unbreakable during the Cold War and was only revealed when KGB agent Reino Häyhänen defected to the United States in 1957, bringing the Straddling Checkerboard technique to Western attention.

Practice Tips for Straddling Checkerboard Mastery

  1. Start simple: Practice Straddling Checkerboard encoding with short words first
  2. Memorize the grid: The VIC configuration (ESTONIAR, 2,6) is the standard Straddling Checkerboard to learn
  3. Parse carefully: Always check if a digit is a blank indicator before decoding in the Straddling Checkerboard
  4. Double-check: Re-encode your decoded message to verify Straddling Checkerboard accuracy
  5. Use our tools: Try the Straddling Checkerboard encoder for practice

Additional Straddling Checkerboard Resources

Expand your knowledge of classical ciphers: