Skip to main content

USB Typing Reconstruction

Challenge​

Content preserved from the original writeup source. Minimal normalization was applied to fit platform format.

Solution​

Original Writeup Content (Preserved)​

USB Typing Reconstruction

Summary​

The correct typed input is recovered from USB device address 11, which emits standard 8-byte HID keyboard reports.

The earlier keypad-click hypothesis was incorrect because it focused on mouse/pointer endpoints from device address 3.

Verified keyboard stream:

  • Device: 11
  • Endpoint: 0x81
  • Report size: 8 bytes
  • HID format: modifier, reserved, key1..key6

Decoding Method​

For each non-empty report:

  • Read byte 0 as modifier bits (Shift handling).
  • Read bytes 2-7 as active key usages.
  • Emit only newly pressed keys relative to the previous report.
  • Translate HID usage IDs to characters with Shift mapping.

Key Events (in order)​

Decoded key presses:

  • U D C T F
  • {
  • k 3 y
  • _
  • S t R 0 K 3 E
  • _
  • 1 S
  • _
  • 7 h e
  • _
  • w A y
  • }

Reconstructed Typed Value​

UDCTF{k3y_StR0K3E_1S_7he_wAy}