In the case of identities/credentials, the blockchain is mostly used as the decentralized timestamp service, used to know the relative orders of events, like wh

In the case of identities/credentials, the blockchain is mostly used as the decentralized timestamp service, used to know the relative orders of events, like when a credential was issued, which key signed the credential, whether the key was revoked by that time, etc. Any public key could be seen as a decentralized identity but you don't have a way to certify if the key was ever rotated, where you usually go to centralized servers, a hacker may compromise a centralized service to change certain information about the public keys but it's unlikely it will compromise Bitcoin, these decentralized identities I mention are on practical terms, mutable, which is where the decentralized timestamp shines. On the auctions, a trust-less smart contract is what shines, as you can get the participants to bid there, and in case of disputes, everyone is able to audit the smart contract to make sure the outcome wasn't manipulated.