Former Mt. Gox CEO Mark Karpelès is developing a low-cost device to detect hidden LTE antennas used in hardware wallet supply-chain attacks without opening the wallets. According to Odaily, the device will emit weak radio waves and measure resonant frequencies to identify potential spy implants; Karpelès plans to publish the circuit board design and specifications so others can build it, and the project remains at the concept stage, with a prototype expected in the coming weeks.