what is a 'soft fork'?
A soft fork is slight change in the protocol of a Blockchain. A soft fork describes the process making past transactions invalid all at once. As existing nodes still recognize new transaction blocks, this mechanism is contrast to the hard fork backwards compatible. A soft fork is coordinated by various parties. How it is executed depends on the governance structure of the cryptocurrency. In general we distinguish between two different types of soft forks:
- Miner executed soft forks
- User activated soft forks
How does a 'soft fork' affect the security?
The more users and miners adapt to new transaction rules, the safer the Blockchain gets. If a part of nodes is not going to accept new rules, confirmation problems will inevitably occur. Users could then potentially create transactions with old rules, that will be verified by parts of old nodes. Holders not being aware of the new nodes would accept transactions that have not been added to the mainchain allowing the sender to doublespend.