broadcastopol

Description

The geopolitical scene has taken a turn for the worse for us recently. One of our allies seems to have modified the communications equipment we initially supplied. Indeed, for several days now, our exchanges have been interrupted. However, one of our agents in the field has intercepted one of their broadcasts (flag.wav.enc). According to our information, it is of tactical importance.

One of our cryptographers told us that the encryption algorithm is used in a classic stream cipher mode and that we know that the clear data are WAV files. His team has also managed to obtain a known plaintext (known.wav/known.wav.enc) for which we know the following:

• IV = 0x000dcf18 ;
• eck = 0x1119EB502F815EB502F8 (eck, Encryption Cipher Key).

Furthermore, for the encrypted message flag.wav.enc intercepted, operational analyses indicate that the value of the IV should be 0x0026b328.

Note : the flag is in FCSC{diffusion_content} format. The content is in English. Its transcription in the flag is in lower case and between each word there is a _. Example: if I hear “You made good today”, the flag is: FCSC{you_made_good_today}.