Five Signatures Expose Zilliqa Keys: Ledger Bug Triggers Transaction Halt

Woofun AI reports that Zilliqa suspended native transactions following the discovery of a critical vulnerability in its Ledger application, which enabled attackers to reconstruct private keys from just five signatures. The network detected on-chain activity indicative of active exploitation on July 19 and confirmed the root cause on July 21, prompting an immediate halt to prevent further asset drainage.

The technical root cause stems from a nonce generation flaw within the signing routine. The process generated 40 bytes of randomness and reduced the result modulo the secp256k1 curve order, but subsequently copied the incorrect 32-byte range into the nonce buffer. This error retained eight zero-padding bytes while discarding eight bytes of actual entropy, fixing the nonce’s highest 64 bits at zero and leaving each value below 2.

Per Woofun AI, the attack vector allows an adversary to combine approximately five affected signatures produced by the same private key to reconstruct the key within seconds on commodity hardware. This rapid reconstruction is achieved using lattice-reduction techniques, turning a theoretical cryptographic weakness into an immediate, actionable threat for any user who has signed multiple native transactions with the compromised device.

A more critical variable is the secondary risk of front-running during the recovery phase. Once native transactions resume, an attacker who has already reconstructed the private key can sign a valid transaction and attempt to front-run the legitimate holder’s transfer. This creates a transaction race where Zilliqa must balance allowing legitimate users to migrate their assets while preventing attackers with identical signing authority from winning the race.

The remediation plan involves a corrected version of the Ledger app, developed in coordination with Ledger, which will restore full-width nonce generation to prevent future exposures.

However, this update cannot secure keys already compromised by signatures recorded on-chain. The vulnerability is specific to the Ledger app’s implementation of native transaction signing; EVM transactions remain unaffected, as do the nonce-generation paths used by the official zilliqa-js, gozilliqa-sdk, and pyzil software development kits.

Currently, native, non-EVM transactions remain suspended as a protective measure. Zilliqa advises any user who has signed native Zilliqa transactions with a Ledger device to await official instructions before taking action, as premature transfers could result in immediate asset loss to compromised accounts.