Given an identifier such as I-Name, username, E-Mail address or URI, it is possible to discover an individual's PDS XDI endpoint.
Methods for discovering an XDI endpoint:
- For I-Names and I-Numbers: XRI Resolution
- For E-Mail addresses: Webfinger
- For URIs: LRDD or DNS CNAME lookup
Example #1: =markus
Using XRI Resolution, the following PDS XDI endpoint can be discovered:
https://xdi.fullxri.com/=!91F2.8153.F600.AE24/
Example #2: E-Mail address
TODO
Example #3: URI
TODO
PDX Lookup Service - Two Stage Lookup
Stage 1: query for PDS Provider
Stage 2: query PDS Provider for XDI endpoint
The purpose of a two stage lookup service is to provide a higher level of security for user personas. In a single stage lookup service (i.e. query PDX with known info and get back an unique XDI endpoint) a user with different personas could be identified as the same user if the same XDI endpoint is used for multiple personas. To avoid this "persona outing" problem, a two stage lookup service is needed where the XDI endpoint is only disclosed after user input. This allows a user to return different personas with different XDI endpoints depending on the context of the request.
Example:
Bob wants to friend Alice through his PDS. Bob does not yet know Alice's PDS endpoint.
- Bob initiates the friend request through an app running against his PDS
- Bob's PDS queries for Alice's PDS Provider through the PDX Lookup Service with known info (e.g. Alice's mobile #) stored in Bob's PDS
- PDX Lookup Service returns Alice's PDS Provider query endpoint; the query endpoint is generic to the PDS Provider and does not identify whether or not Alice exists
- Bob's PDS queries Alice's PDS Provider by sending Alice's graph of known info (mobile #, name, etc.) ; same query as the PDX Lookup Service query
- Alice's PDS Provider acks with no indication of whether or not Alice exists
- Alice's PDS Provider notifies her of the friend request
- Alice now has the option of accepting the request and selecting a specific persona (e.g. Alice at work) or denying the request
- If Alice accepts the request, Bob's PDS gets notified of Alice's XDI endpoint and friend request acceptance; if she does not accept, nothing happens
Note: Super users running their own PDS Provider will need to be aware of persona linking security issue and run distinct personas on different domains.
Webfinger Support for I-Names
The xri2xrd.net tool can be used to make I-Names Webfinger-able, e.g.: =markus@xri2xrd.net
Webfinger Tools
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