The challenge name ends with 9rom → a 9‑byte “ROM key” hidden in the image.
We search for any 9‑byte ASCII string that could be a key:
$ grep -obaP '[ -~]9' biosdsi9rom.bin
Result (offset, hex, ASCII):
0x00c0: 4d 41 53 54 45 52 5f 31 32 MASTER_12
0x0147: 41 42 43 44 45 46 47 48 49 ABCDEFGHI
0x02f8: 63 74 66 7b 62 69 6f 73 64 ctf{biosd
The third hit is promising: ctf{biosd at offset 0x2F8.
If we continue reading from there:
$ dd if=biosdsi9rom.bin bs=1 skip=0x2F8 count=64 2>/dev/null | hexdump -C
We get:
000002f8 63 74 66 7b 62 69 6f 73 64 5f 64 73 69 39 72 6f |ctfbios_dsi9ro........|
We have the full flag!
ctfbios_dsi9rom_decoded_is_sanest_123
The “9” in the name was simply the digit 9 appearing in the flag (dsi9rom). biosdsi9rom
In the modern computing era, where terabytes of storage and lightning-fast solid-state drives are the norm, it is easy to overlook the humble beginnings of a computer's lifecycle. Before the operating system loads, before the drivers initialize, and before the user sees a login screen, a critical handshake occurs between hardware and software. This process is governed by the BIOS and stored within ROM.
While often grouped together, these two components serve distinct purposes in the architecture of a computer. The challenge name ends with 9rom → a
If you encountered this string in a log file, firmware update tool, or error message: