A Fine Cipher

Overview

• 137 Points / 280 Solves

• Overall difficulty for me (From 1-10 stars): ★☆☆☆☆☆☆☆☆☆

Background

We have intercepted a message from a suspicious group. Can you help use break the code and reveal the hidden message?

Encryped Message: JSNRZHIVJUCVIVFCVYBMVBDRZCXRIVBINCORBCSFHCBINOCRMHBD

NOTE: Make sure you wrap the flag

Find the flag

Hmm… That message looks like encoded in base32… However, it said “Encryped”…

After fumbling around, I found that the answer is in the challenge’s title: “Afine Cipher”

The affine cipher is a type of monoalphabetic substitution cipher, where each letter in an alphabet is mapped to its numeric equivalent, encrypted using a simple mathematical function, and converted back to a letter.

Then, find a online tool that brute force the encrypted message. I’ll use dcore.fr:

Found it!

• Flag: RS{IFYOUAREINTERESTEDCHECKOUTMORECRYTPOCTFSATCRYPTOHACK}

Conclusion

What we’ve learned:

1. Deciphering Affine Cipher