Reasonably Strong Algorithm

RSA strikes again!

File: actf2020-rsa.txt

Recon

We solved it by using Ganapati/RsaCtfTool

./RsaCtfTool.py \
    --uncipher 13612260682947644362892911986815626931 \
    -e 65537 \
    -n 126390312099294739294606157407778835887
[+] Clear text : b'\x00actf{10minutes}'

Flag

actf{10minutes}