# kaal:claim:3441904-024

**Claim.** Hard forks can reintroduce the double spend problem, because wallets, merchants, and users running the previous code deem the new code invalid and cannot detect spending on it, so coins spent in a new block could be spent again on an old block.

**Type.** mechanism  **Support.** argued

**Holds when.**

- hard forks only, since old nodes read both block versions after a soft fork

**Source quote.**

> Because wallets, merchants, and users running the previous code deem the new code invalid and thus cannot detect the spending on the new code, cryptocurrencies spent in a new block could be spent again on an old block.

**From.** Wulf A. Kaal, *Blockchain-Based Corporate Governance* (2019), III.5 Socially Optimal Forks, page 21

**Cite as.** Wulf A. Kaal, Blockchain-Based Corporate Governance (2019). SSRN: https://ssrn.com/abstract=3441904

**Verify.** sha256 of source PDF `e6b562527f7f19accaa35491db0a0db168b6a936755e1dca424e9f30bee7a815` at https://raw.githubusercontent.com/wulfkaal/Academic-Papers/main/papers/pdf/Kaal%20-%202019%20-%20Blockchain-Based%20Corporate%20Governance.pdf

**Failure mode.** fork-induced-double-spend  (family: consensus-and-protocol-attack)

**Topics.** consensus-and-security, economics

**Keywords.** hard-fork, double-spend, protocol-upgrade, economic-loss

**Related claims.**

- restated_by: https://wulfkaal.github.io/claims/3808873-036
- extended_by: https://wulfkaal.github.io/claims/3652481-018

**Canonical form.** This markdown file is the canonical hashed representation of the claim. Its sha256 is the content hash used for attestation.