Non-blockchain use

[clehner]

did:pkh is for identifiers based on hashes of public keys. Existing use cases use blockchain account addresses (which are public key hashes) and the blockchainAccountId property as part of the verification relationship. Is there desire for use of did:pkh with public key hashes that do not fit into blockchainAccountId/CAIP-10? Currently did:pkh uses CAIP-10 for the whole namespace, except for some prefixes allowed for legacy reasons that predated settling on using CAIP-10 in the DID: https://github.com/w3c-ccg/did-pkh/blob/main/did-pkh-method-draft.md#appendix-legacy-support

Some possible non-blockchain public key hashes

• OpenPGP fingerprint
  • https://datatracker.ietf.org/doc/html/rfc4880#section-12.2
  • Hash of data structure that includes timestamp
    • Trezor GPG agent uses 0 for default timestamp for deterministic generation
  • Proposed CAIP (gpg): Draft: Add GPG namespace ChainAgnostic/CAIPs#66
• SSH public key fingerprint hash
  • Hash of SSH public key format
  • https://unix.stackexchange.com/questions/408338/how-to-compare-different-ssh-fingerprint-public-key-hash-formats
  • SSHFP DNS resource record: https://datatracker.ietf.org/doc/html/rfc4255#section-3.1.2
  • Used for hashing in ~/.ssh/known_hosts (confirming server identity)
  • Used in list output of ssh-agent
• Public Key Pinning Extension for HTTP: hash of SubjectPublicKeyInfo
  • https://www.rfc-editor.org/rfc/rfc7469#section-2.1.1
  • https://stackoverflow.com/questions/40404963/how-do-i-get-public-key-hash-for-ssl-pinning
• Android Debug Bridge (adb) RSA key fingerprint
  • Used for confirming that a computer can operate an Android phone via adb
  • https://developer.android.com/studio/command-line/adb#Enabling
  • https://old.reddit.com/r/androiddev/comments/1ym70d/rsa_key_fingerprint_android_device_gives_for_my/
• JWK Thumbprint (URI)
  • Hash of canonicalized minimized public key JWK
  • https://datatracker.ietf.org/doc/html/rfc7638
  • https://datatracker.ietf.org/doc/html/draft-ietf-oauth-jwk-thumbprint-uri
• DIF Sidetree reveal value
  • Hash of public key JWK with optional nonce property
  • Intended to be single use; probably not useful for a DID
  • https://identity.foundation/sidetree/spec/v1.0.0/#reveal-value
  • https://identity.foundation/sidetree/spec/v1.0.0/#public-key-commitment-scheme

Are there any others that might be relevant for did:pkh? How might they be expressed in verification material?