MoreText

Platform: spbctf | Category: Crypto | Type: Challenge | Difficulty: Medium | OS: NA | Author: XESXOR | Date: 2026-03-08 | Status: Solved Techniques: Build substitution table from known pairs, Identify source text (Wikipedia article), Known plaintext attack on substitution cipher

Summary

Task: Monoalphabetic substitution cipher on Merkle-Hellman Wikipedia article. Solution: Identify source text, build mapping from known plaintext pairs to recover the alphabet permutation.

MoreText — cryptokids20

Description

Monoalphabetic substitution cipher on Merkle-Hellman Wikipedia article.

Solution

Identify source text, build mapping from known plaintext pairs. Flag is the alphabet permutation. ‍​‌‌​​‌​​​‌‌​​‌​​​​‌‌​‌​​​​‌‌‌​​‌​​‌‌​​​‌​​‌‌‌​​​​​‌‌​‌‌​​​‌‌​​​​‍