Vigenere Stego Hunt

🔐 Can you crack the cipher that stumped cryptographers for 300 years?

Challenge 23 Nov 2025 Pro Exclusive Solution Available

Master spies have hidden their most sensitive secrets using this legendary polyalphabetic cipher, but there's a twist - the key itself is concealed within innocent-looking images! 🖼️ Combine classical cryptanalysis with modern steganographic techniques to uncover layers of hidden information. 🕵️ This challenge demands both historical cryptographic knowledge and cutting-edge digital forensics skills to reveal the ultimate secret! 🔍

Flags

Points

86%

Success Rate

Start Your Challenge

~1-2 min setup

Dedicated server

Private instance

Industry standard

This solution is for Flags Mode

This walkthrough explains how to hack the lab and capture the flags. For help with Learning Mode questions, use the Request Hint button next to each question.

Challenge

🔐 Vigenère Stego Hunt - Complete Solution

Objective: Extract the hidden key from the image using steganography, then use it to decrypt the Vigenère cipher and reveal the flag.

🔍 Step 1: Steganographic Analysis

The challenge provides an image file that contains hidden data using LSB (Least Significant Bit) steganography. Extract the hidden key using steganographic tools:

Method 1: Using zsteg
zsteg secret_key.png

Method 2: Using steghide
steghide extract -sf secret_key.png

Method 3: Using Python script
Extract LSB data from the red channel of image pixels to reveal hidden text.

🔍 Step 2: Extracting the Vigenère Key

The steganographic analysis reveals the hidden key: CRYPTOKEY

Key Discovery: The key 'CRYPTOKEY' is embedded in the least significant bits of the image pixels. This demonstrates how steganography can securely distribute cipher keys.

🔍 Step 3: Vigenère Cipher Decryption

With the key 'CRYPTOKEY', decrypt the ciphertext 5E22R314BS144Y75853SN168F8BFVBQY using standard Vigenère decryption:

Decryption Process:
Ciphertext: 5E22R314BS144Y75853SN168F8BFVBQY
Key: CRYPTOKEY (repeated)
Result: 5C22A314DD144F75853ED168B8DDEDBF

Online Tools:
• https://www.dcode.fr/vigenere-cipher
• https://cryptii.com/pipes/vigenere-cipher

🔍 Step 4: Formatting the Flag

The decrypted text 5C22A314DD144F75853ED168B8DDEDBF is the UUID without hyphens. Add hyphens at the standard UUID positions:

Final Flag: The complete UUID flag is revealed after adding hyphens to the decrypted text.

📚 Learning Points

Steganography: LSB techniques for hiding data in images
Classical Cryptography: Vigenère cipher mechanics and decryption
Multi-layer Security: Combining steganography with cryptography
UUID Format: Understanding standard UUID structure with hyphens

Security Note: This challenge demonstrates how multiple security layers can protect sensitive data, requiring knowledge of both steganographic and cryptographic techniques.