Hi,
Firstly, I would like to share with you the solution of the problem in the CRYPTO category by leaving the first week of the BattleWare CTF Competition, which is a short-term but fun and at the same time a challenging.
When we examine the “br34k1t.txt” text file given to us in the question, we see that it contains an encrypted text.
Encrypted Text : eGlBPCx7Sk5uJFsreXYyZjB8WUxNOl97cCNPZE9CSEp3S3p6Qz9qRyhNcCFYW010
We can use the site https://md5hashing.net/ to find out which type of encrypted.
You can view the match here: https://md5hashing.net/hash/base64/mcPHSn7xFtEM3nKBW
We understand that the encryption method that matches our encrypted text is Base64. We can use the https://www.base64decode.org/ site to decipher the Base64 encrypted data.
Base64 decrypted data: xiA<,{JNn$[+yv2f0|YLM:_{p#OdOBHJwKzzC?jG(Mp!X[Mt
When we examine the decrypted data, we see that we have encrypted data again. We use the site https://cryptii.com/ to find out which encryption method this data is encrypted with.
If we examine the library of the site one by one, we can understand that it is encrypted with the Vigenere Encryption method. However, in the vigenere encryption method, we need a key to be able to decrypt it, and when we entered the key as “BATTLEWARE”, we got another encrypted data again. (In this part, I was obviously about to give up, but seeing the second hint “it was encrypted 3 times.” it motivated me to try again.)
Encrypted Text: wiH<,{QCj$[+cv2o0|UKM:_{w#VsKFHSsJzgJ?yC(Qp!G[Is
I thought this data was encrypted with vigenere and tried again, but since I knew I tried it for the third time, we should have captured the flag this time, this was our last data and it should have been encrypted with a different encryption method. When we examine the encryption methods again, we can see the list of tools with Character Encryption method by browsing the list on https://www.dcode.fr/tools-list.
When we examine the appropriate ones for our encrypted data in the Character Encryption section, you can examine the image below.
Examining the encryption methods one by one, we find that it is encrypted with Base91. By decrypting our encrypted data with Base91 and we captured the flag.
Flag: Flag{c0ngr4ts!_this_is_th3_crypt0_fl4g}
Thank you for your time 😊
