Bitcoin Gold Hack

Reported exposure $18.0M
Bitcoin Gold
Majority-hash-power double spend

What happened

Bitcoin Gold experienced repeated majority-hash-power attacks against exchanges during May 2018. Its team reported a period of about three and a half days, ending with the last known attempt on May 19. The attacks used chain reorganizations to reverse exchange deposits after assets had been credited.

Bitcoin Gold said it could not determine how many attempts succeeded or which exchanges were affected.

Technical root cause

Majority mining power enabled competing chain histories and exchange double-spends. The attack concerned proof-of-work consensus and deposit finality.

How it happened

  1. The attacker controlled sufficient mining power to construct a competing Bitcoin Gold chain.
  2. BTG deposits were presented to exchanges while a conflicting chain was mined privately.
  3. Publishing the competing chain could reverse credited deposits, enabling exchange double-spends.
  4. Exchanges increased confirmation requirements or suspended deposits, while the Bitcoin Gold team monitored reorganizations and alerted exchanges.

Protocol details

Classification Consensus
Protocol Type Chain
Protocol links Website @bitcoingold

Evidence

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