rsa_oracle
Can you abuse the oracle? An attacker was able to intercept communications between a bank and a fintech company. They managed to get the message (ciphertext) and the password that was used to encrypt the message.
The files serve different purposes: password.enc contains an RSA-encrypted password, while secret.enc contains the encrypted message. The oracle offers encryption and decryption operations, as the sample round trip with a shows.
nc titan.picoctf.net 59179
The script output shows the recovered password as 60f50. Use it with the OpenSSL AES-256-CBC decryption command shown below to read secret.enc. The recovery script itself is not included in this note, so the intermediate RSA manipulation is not documented here.
Got the flag!
This post is licensed under CC BY 4.0 by the author.