Crypto 8

Crypto 8¶

📚 Category: Crypto
🎯 Points: 300
📝 Description: Use flagCheck to input the flag you get from the challenge to get the actual flag

✍️ Writeup¶

We one file:

chall.txt

Cipher text: EKEMQ XI LEWI CIESQIH ULEU BVS USEQTPMTTMBQT ESI FIMQK PBQMUBSIH. ET E SITVCU XI ESI GLEQKMQK ULI IQGSDAUMBQ PIULBH EKEMQ. ULI QIX OID JBS QIYU PIIUMQK XMCC FI ABCDKBQ. MU MT MPAISEUMWI ULEU DBV ECC EUUIQH ECC PIIUMQKT JSBP LISI BQ MQ.

This is a Monoalphabetic Substitution Cipher

ABCDEFGHIJKLMNOPQRSTUVWXYZ
POLYABCDEFGHIJKMNZRSTUVWXQ

AGAIN WE HAVE LEARNED THAT OUR TRANSMISSIONS ARE BEING MONITORED. AS A RESULT WE ARE CHANGING THE ENCRYPTION METHOD AGAIN. THE NEW KEY FOR NEXT MEETING WILL BE POLYGON. IT IS IMPERATIVE THAT YOU ALL ATTEND ALL MEETINGS FROM HERE ON IN.

Let's check with flagCheck

hacker@csawctf2011~crypto-300-8:/challenge$ ./flagCheck
Enter the flag: POLYGON
Correct flag!
pwn.college{REDACTED}