Classic, yet complicated!

Platform: HackTheBox | Category: Cryptography | Difficulty: Easy | Author: D3v0o0Nu11 | Date: 2026-02-10

Description

Find the plaintext, the key is your flag! Flag format : REDACTED

Solution Approach

Core idea: Identify the weakness from source review or fingerprinting first. Iterate with incremental payloads instead of guessing.

Steps

1. First, unzip the .zip file given.

2. Let's paste the ciphertext to this website, so we know what ciphertext is this.

3. It's vigenere cipher! Now let's decode that using dcode.fr.

4. Based on the plaintext we got, we know that the key is HELLOWORLD, but based on the description, let's paste the string in lowercase as the flag.

5. Got the flag!

Flag

REDACTED

Lessons Learned

1. Identify the weakness from source review or fingerprinting first.
2. Iterate with incremental payloads instead of guessing.
3. Reuse the same pattern in future engagements.