CTFs | 404CTF2023 | Cryptography | ASCON Marchombre

ASCON Marchombre

Important information:

nonce: 0

message chiffré: ac6679386ffcc3f82d6fec9556202a1be26b8af8eecab98783d08235bfca263793b61997244e785f5cf96e419a23f9b29137d820aab766ce986092180f1f5a690dc7767ef1df76e13315a5c8b04fb782

Données associées: 80400c0600000000

I found a very cool github repo for ASCON. After modifying the code a little bit I got the decoded msg.

Code after modifying code

$ python3 ascon_modified.py 
=== demo encryption using Ascon-128 ===
key:           0x00456c6c616e61206427416c2d466172 (16 bytes)
nonce:         0x00000000000000000000000000000000 (16 bytes)
ass.data:      0x80400c0600000000 (8 bytes)
decrypted_msg: 0x4c6120766f6965206465206c276f6d6272650a45742064752073696c656e63650a3430344354467b563372355f6c345f6c756d31e872332e7d0a456c6c616e61 (64 bytes)

Using cyberchef to get the flag:

Flag: 404CTF{V3r5_l4_lum1èr3.}