Category: forensics,crypto
Author: _Roko'sBasilisk_
Do you know that Shatranj is a proto-version of chess? But anyway, it's time to move on to modern stuff.
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Reveal Spoiler
The purpose of this challenge is to disect and isolate the gRPC messages in order to get the iv, encrypted_flag and key so that they can be trivially decrypted using AES in CBC mode.
The solution is as follows:
- Open pcap file and isolate relevant gRPC protocol packets (can be identified from port numbers and data)
- Use the provided proto file to have wireshark disect the packets for you. (See https://grpc.io/blog/wireshark/)
- Get iv, ciphertext (flag) and key and use python or any other apprpriate tool to decrypt the ciphertext and get the flag.