I would like to give my and KILT’s two cents here. I know not everyone likes DIDs, but we do think they fulfil some of the issues that have also been discussed in this thread. We are definitely super interested in the development of a generalised way to generate and verify storage proofs, as we are in the development of the Interchain Proof of Oracle. We think a DID can fulfil the job of abstracting over specific accounts, allowing, for instance, multiple accounts, potentially from different chains, to be linked under the same DID (feature has been live for months already).
Given there is a way for target chains to retrieve the state of a DID or simply verify a Merkle proof over some representation of the DID document, it becomes quite easy to do some of the things mentioned here, most importantly probably having a single source of truth for someone’s identity, and being able to link accounts (including multiple proxies) to the same DID and operate as such.
Clearly this does not take into account privacy, but we think that there are use cases where linking multiple bits of information is actually beneficial, with the most important use case being linking multiple collator accounts from multiple blockchains under the same umbrella, which we have identified as being a Decentralised Identifier, or DID, which also provides a standard and especially extensible way of exposing information.
This is really easy and we support this. Doing merke proofs is really easy. Assuming you don’t mean that you want to generate them from the runtime. For things in the current state it should also be relative easily possible to create a proof. However, I don’t know if we should do this on chain and not in some offchain context.
On the side, I wanted to ask @bkchr if there have been any metrics on the block weight and time that the runtime takes to generate merkle proofs depending on the size of the input data, be it passed as a parameter e.g. via some extrinsic or being retrieved from the storage. In any case, what would be the best place to look for existing code to re-use or to take inspiration?