Mary

Platform: CUSTOM | Category: Crypto | Type: Challenge | Difficulty: Easy | OS: N/A | **Author: XESXOR Techniques: Historical cipher recognition, Mary Stuart / Babington Plot cipher decryption, Symbol-to-letter substitution

Summary

Walkthrough of the CUSTOM Crypto Mary. File: Mary.png — image with symbols

Description

Похож на шифр средневековья... Он достаточно стойкий или кому-то он стоил головы?

(Looks like a medieval cipher... Is it strong enough or did it cost someone their head?)

File: Mary.png — image with symbols

Analysis

Historical Context

The task name "Mary" and description contain clear hints:

1. "Medieval cipher" — points to a historical cipher from the 16th century
2. "Cost someone their head" — direct reference to execution
3. "Mary" — the name points to Mary Queen of Scots ‍​‌‌​​‌​​​‌‌​​‌​​​​‌‌​‌​​​​‌‌‌​​‌​​‌‌​​​‌​​‌‌‌​​​​​‌‌​‌‌​​​‌‌​​​​‍

Mary Stuart and the Babington Plot

Mary Stuart (1542-1587) — Queen of Scotland, was imprisoned by Elizabeth I. In 1586, she participated in the Babington Plot — an attempt to assassinate Elizabeth I and place Mary on the English throne.

Mary used a nomenclator — a combined cipher:

• Symbols for alphabet letters
• Special symbols for frequent words and names
• Nullifiers (empty symbols for obfuscation)

The cipher was broken by cryptanalyst Thomas Phelippes, which led to the exposure of the plot and Mary Stuart's execution in 1587. ‍​‌‌​​‌​​​‌‌​​‌​​​​‌‌​‌​​​​‌‌‌​​‌​​‌‌​​​‌​​‌‌‌​​​​​‌‌​‌‌​​​‌‌​​​​‍

Cipher Identification

The image Mary.png contains symbols from the Babington cipher — characteristic geometric shapes and symbols used in Mary Stuart's correspondence.

Solution

Step 1: Symbol Recognition

The symbols in the image correspond to Mary Stuart's cipher alphabet:

Each symbol = one letter of the Latin alphabet

Step 2: Decoding via dcode.fr

Used online decoder:

• URL: https://www.dcode.fr/mary-stuart-code
• Uploaded the image or entered symbols
• Automatic matching with the known Babington alphabet ‍​‌‌​​‌​​​‌‌​​‌​​​​‌‌​‌​​​​‌‌‌​​‌​​‌‌​​​‌​​‌‌‌​​​​​‌‌​‌‌​​​‌‌​​​​‍

Step 3: Result

Decoded text: REDACTED

This is a wordplay:

• "What about head?" — reference to the head
• Allusion to the fact that breaking this cipher cost Mary Stuart her head (execution by beheading)

Mary Stuart Cipher Alphabet

The Babington cipher uses unique symbols for each letter:

Full alphabet available at dcode.fr

Resources

‍​‌‌​​‌​​​‌‌​​‌​​​​‌‌​‌​​​​‌‌‌​​‌​​‌‌​​​‌​​‌‌‌​​​​​‌‌​‌‌​​​‌‌​​​​‍

• dcode.fr — Mary Stuart Code
• Wikipedia — Babington Plot
• Wikipedia — Mary, Queen of Scots

Historical Ciphers in CTF

Other historical ciphers that may appear:

Key Takeaways / Lessons

• Mastering Historical cipher recognition, Mary Stuart / Babington Plot cipher decryption, Symbol-to-letter substitution was key to this challenge.
• Always check for common misconfigurations and verify assumptions.

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Crafted by XESXOR Research • 2025-12-30 • CUSTOM • Mary • Difficulty: Easy