A computer-implemented method (600) and system (1) for verifying ownership of a computer software after installation and prior to execution using a distributed hash table (13) and a peer-to-peer distributed ledger (14). This may be the Bitcoin blockchain or an alternative implementation. The method includes determining (610) a second user public key associated with a second user (24) from a transaction record stored on the peer-to-peer distributed ledger (14). A second public key associated with the second user may be determined (620) from an entry on the distributed hash table (13). The method further includes comparing (630) the second user public key and the second public key, and verifying (640) the ownership of the computer software based on the comparing of the second user public key and the second public key.