Bitkey app used a non-cryptographic random generator for contact enrollment

On 2 August 2026 Bitkey, Block’s bitcoin wallet, disclosed a bug reported a day earlier by the X user @1440000bytes. Bitkey’s security updates page lists the same issue as BKS.2026.08.D and credits the reporter as floppy.md.

According to Bitkey, its mobile app generated the short secrets used to enroll Recovery Contacts and inheritance beneficiaries, and nonces in second-generation action proofs, with kotlin.random.Random, a general-purpose generator not designed for cryptographic use. Under narrow conditions, an attacker who observed enough related outputs could reconstruct its state and predict a later enrollment secret. Bitkey says the bug is in the app, not the hardware or firmware, and only affects second-generation users who used relationship enrollment, a flow launched in late April 2026.

Bitkey states the bug does not weaken the hardware key, the server key or spending keys, and that because wallets use 2-of-3 signing even a successful exploit would not give enough to move funds; it rates the practical risk for Recovery Contacts as none and for beneficiaries as highly improbable, requiring extensive access to Block’s infrastructure. It says its server logs show no insider activity of the kind an attack would leave. The fix switches to a cryptographically secure generator; Bitkey’s security updates page lists it in app 2026.11.2. Crypto Briefing reports the patch was submitted to both app stores on 1 August and that Bitkey held a public X Space on the issue on 2 August.

What Bitkey advises:

• Keep the app updated.
• Second-generation users with an inheritance beneficiary should re-enroll the beneficiary after updating.