SlowMist Rebuilds Qubic Private Key From Six Header Values in Local Test

SlowMist reconstructed a Qubic wallet’s private key in a local test using six consecutive network header values, revealing a possible route from observable traffic to a weak wallet seed.

The finding follows the theft of about 2.94 trillion QU, units of Qubic (QUBIC), from 1,404 wallets. The transfers occurred between 7:42 and 9:26 p.m. ET on Oct. 17 (23:42 UTC Oct. 17 to 01:26 UTC Oct. 18). The affected wallets had seeds generated with insufficient randomness.

Before a patch, Qubic’s web wallet used Math.random() to create seeds and to fill a request-header field called dejaVu. A seed is the secret used to derive a wallet’s keys. In the local test, six consecutive header values and the right alignment of generator calls allowed SlowMist to reconstruct the generator’s internal state, recreate a seed and match its private key. Four or five values left multiple possible states.

The test modeled the V8 random-number generator. Its result depends on access to the relevant traffic, consecutive observations and call alignment; it does not establish that the method works for every affected device or that the thieves used it in the October theft.

The wallet’s connection to the default web bridge is encrypted, while packets sent from that bridge to network peers travel in plaintext. That bridge-to-peer traffic is the potential point of observation in the tested route.

Qubic’s web wallet version 4.26.4 switched new seed creation to crypto.getRandomValues(). The dejaVu header still uses Math.random(), but new seeds no longer come from that random stream. The change does not strengthen seeds created before the patch.

Qubic halted its network and immobilized 87.1% of the stolen tokens. Those tokens have not been returned to their owners. A recovery decision rests with Qubic’s Computor quorum.