A “tamper-proof” currency wallet just got trivially backdoored by a 15-year-old

Enlarge (credit: Saleem Rashid)

For years, executives at France-based Ledger have boasted their specialized hardware for storing cryptocurrencies is so securely designed that resellers or others in the supply chain can't tamper with the devices without it being painfully obvious to end users. The reason: "cryptographic attestation" that uses unforgeable digital signatures to ensure that only authorized code runs on the hardware wallet.

"There is absolutely no way that an attacker could replace the firmware and make it pass attestation without knowing the Ledger private key," officials said in 2015. Earlier this year, Ledger's CTO said attestation was so foolproof that it was safe to buy his company's devices on eBay.

On Tuesday, a 15-year-old from the UK proved these claims wrong. In a post published to his personal blog, Saleem Rashid demonstrated proof-of-concept code that had allowed him to backdoor the Ledger Nano S, a $100 hardware wallet that company marketers have said has sold by the millions. The stealth backdoor Rashid developed is a minuscule 300-bytes long and causes the device to generate pre-determined wallet addresses and recovery passwords known to the attacker. The attacker could then enter those passwords into a new Ledger hardware wallet to recover the private keys the old backdoored device stores for those addresses.

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