Presented at
DEF CON 33 (2025),
Aug. 8, 2025, 10 a.m.
(45 minutes).
I’m sure you’ve heard of MIDI – it’s a protocol and file format that’s used to exchange audio generation data such as “note on” and “note off” events. But what if I told you that there’s a MIDI implementation out there in the wild that, when excited in just the right ways, can do stuff the original product designers never intended to do? In this talk, we’ll dive into the wonderful world that is hardware reverse engineering. We’ll explore what JTAG and UART are and how we can use them to hack modern digital devices. We’ll dump the firmware of a Yamaha music keyboard and discover what is essentially a backdoor in the MIDI implementation – and exploit it to play Bad Apple on the keyboard’s dot matrix LCD.
References:
[Architecture of Yamaha entry-level synths](https://sandsoftwaresound.net/swl-micro-architecture/)
[MIDI specification](https://midi.org/spec-detail)
[MIDI SysEx ID allocation table](https://midi.org/sysexidtable)
[ARM7TDMI Technical Reference Manual](https://developer.arm.com/documentation/ddi0084/f)
Presenters:
-
Anna portasynthinca3 Antonenko
Anna “porta” has been playing around with Arduinos and whatnots since about 2017, when she was 13 years old. She’s made countless hobbyist projects with AVR, STM32 and ESP32 microcontrollers to learn more about the wonderful world of digital electronics. Today, she’s a professional embedded firmware engineer with an interest in hardware reverse engineering, operating system development and distributed fault-tolerant systems.
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