Forced Address Reuse

Forced address reuse is the Bitcoin Wiki's name for a tracking trick that only works on an address you have used before. An adversary sends a small payment, a few hundred satoshis of dust, to addresses that have already appeared on the chain. Nothing happens yet. The bet is on your next spend: if your wallet picks up the crumb as an input alongside your real coins, the transaction declares that every input has one owner, and the adversary's address clustering grows to match. The Wiki says this "is sometimes incorrectly called a dust attack"; the dust attack entry covers the press name.

A wallet that hands out a fresh address for every payment has no used-and-still-receiving address for a crumb to land on. The attack manufactures address reuse you did not choose, so the defense is about what you do next. It splits in two, as the Wiki splits it:

• If the crumb landed on an address you had already emptied, never spend it. Freeze it with coin control. Bitcoin Core's lockunspent gained a persistent option in PR #23065 (merged 2021, shipped in 23.0 in 2022) so the lock survives a restart.
• If it landed on an address that still holds your coins, spend everything at that address together, crumb included, in one transaction with no inputs from anywhere else. Those coins were already linked by sharing an address, so spending them together adds nothing new; leaving the crumb behind keeps the trap armed.

Bitcoin Core's answer came in three releases. Version 0.17.0 (2018) added -avoidpartialspends, which spends all coins on one address together even at a higher fee; its release note admitted the gap: "If someone were to send coins to an address after it was used, those coins will still be included in future coin selections." Version 0.19.0.1 (2019) closed that gap with the avoid_reuse wallet flag, which marks every address the wallet has spent from and skips coins sent there afterwards; PR #13756 gave the reason: without it "a payer could otherwise begin tracking a payee's wallet by regularly peppering a known UTXO with dust outputs". The flag is off by default; see Avoid Reuse (Bitcoin Core). Since 0.21.0 (2021) the wallet groups same-address coins by default whenever that costs no extra fee (PR #14582).

There is a newer reason to care. On bitcoin-dev on 19 April 2026, discussing post-quantum output types, Matt Corallo noted that "dusting attacks could trigger many wallets to reveal a public key too soon": a crumb that provokes a spend from a hash-protected address puts its key on the chain for good. See Public Key Exposure for why that matters, and Privacy on Bitcoin for the clustering it feeds.