SlowMist Security Chief Information Security Officer Analyzes Suspected Screen Theft Path of Ledger
SlowMist Security Chief Information Security Officer 23pds stated that if the modification of the Ledger device PCB is as described by former Mt. Gox CEO Mark Karpelès, then the attacker would possess a considerable level of technical skill.
The attack process may be: the wallet generates the mnemonic phrase within a secure element (SE), then displays the mnemonic on the screen for the user to write down; a malicious module retrieves the displayed content through screen data lines such as SPI, records the complete mnemonic, and then sends the data to the attacker via LTE/eSIM, ultimately leading to the theft of user assets.
The role of the secure element is to prevent the private key from being directly read or exported, but it cannot stop external modules from obtaining the information currently displayed on the screen. The above analysis is based on the premise that the PCB has indeed been modified as described, and the relevant attack paths and hardware implantation still require independent verification.
Karpelès previously disclosed that a Ledger hardware wallet he received appeared to have a spy module implanted. The device came from Malaysia, the outer packaging was intact, and it was difficult to immediately detect abnormalities after opening, as the implant was hidden in the position where the screen's original cushioning pad should be.
Karpelès further explained that the module contains LTE communication components, an antenna, an eSIM, and a microcontroller connected to the Ledger SPI bus, which can analyze the characters displayed to the user and send relevant data after the mnemonic setup is completed. The SPI bus is the channel through which Ledger transmits display data to the screen.
This module may still pass genuine device verification since it does not directly contact the secure element and firmware. Karpelès stated that he will further analyze the SIM card and microcontroller within the module, including extracting firmware. Currently, Ledger's official investigation is ongoing, and the relevant hardware implantation has not yet been independently confirmed.
If the attack path is valid, funds could be remotely transferred after the user completes the mnemonic setup, with the parties under pressure being users who purchased the device through suspicious channels and the trust in the hardware wallet supply chain, while the beneficiaries would be the attackers who possess the mnemonic.
Source: Public Information
ABAB AI Insight
SlowMist has long been engaged in blockchain security research and incident response, with 23pds, as its Chief Information Security Officer, publicly analyzing hardware wallets, supply chain, and side-channel risks multiple times. Mark Karpelès previously operated Mt. Gox and has turned to hardware security observation after the exchange's collapse, publicly dismantling and describing the internal structure of the device sourced from Malaysia.
Karpelès demonstrated the implant location and component composition through physical disassembly, while 23pds mapped the observed hardware characteristics to specific data flow paths: the secure element generates the seed, the screen displays plaintext, external modules passively listen to SPI, and LTE/eSIM transmits externally. This path bypasses the secure element's protection of the private key, shifting the attack surface to the plaintext bus from the MCU to the screen.
Similar historical cases include instances of counterfeit hardware wallets where the main control chip was replaced and wireless modules were implanted, as well as side-channel techniques in consumer electronics supply chains that steal displayed content through screens or interface lines. The current hardware wallet industry is transitioning from "trusting secure elements + official channels" to "verifying the entire delivery chain and physical integrity".
This essentially combines technological substitution with industrial chain reconstruction: attacks no longer attempt to breach the secure element itself but implant bypass listening at the stage where the secure element outputs plaintext. The mechanism is that the mnemonic must appear once in a human-readable form on the screen, creating a brief plaintext window that becomes a feasible entry point for supply chain attacks; once the mnemonic is intercepted, any subsequent device-side protection becomes ineffective, forcing the industry to shift from single-chip trust to full-link physical and delivery verification.
ABAB News · Cognitive Law
The secure element protects the private key but not the screen plaintext.
Intact packaging does not equal intact internals.
Displaying plaintext once opens the attack window.