This talk will demystify Decentralized Identifiers (DIDs) via the simple Bitcoin Reference (BTCR) DID Method. Kim will introduce the basics of DIDs and show how they work in action through demos of the creation/updating and resolution process in BTCR. We'll build on this knowledge by discussing advanced features enabled by DIDs, along with a brief survey of other DID methods. By the end of the talk, you'll be able to create and resolve your own BTCR DIDs through the live BTCR playground.

1. twitter.com/kimdhamilton
DIDs Demystified
A hands-on intro to DIDs via the BTCR DID Method
June 6, 2018
SSIMeetup.orghttps://creativecommons.org/licenses/by-sa/4.0/
Kim Hamilton Duffy
CTO of Learning Machine, Principal Architect of Blockcerts and co-chair W3C Credentials
Community Group

2. 1. Empower global SSI communities
2. Open to everyone interested in SSI
3. All content is shared with CC BY SA
SSIMeetup.org
Alex Preukschat @SSIMeetup @AlexPreukschat
Coordinating Node SSIMeetup.org
https://creativecommons.org/licenses/by-sa/4.0/
SSIMeetup objectives
6 June 2018

3. How I got involved with SSI
● CTO of Learning Machine
● Principal Architect of Blockcerts
● Open source/open standards for blockchain verification of
credentials
● Open Badges and Verifiable Credentials Alignment
● JSON-LD signatures and suites
● RWoT => Involvement with Decentralized Identifiers (DIDs)
and the BTCR Method Spec
● Co-chair W3C Credentials Community Group
SSIMeetup.org

4. Orientation
From Drummond Reed’s SSI Meetup 2 (DIDs)
Method DID prefix
Sovrin did:sov:
Bitcoin Reference did:btcr:
Ethereum uPort did:uport:
Blockstack did:stack:
Veres One did:v1:
IPFS did:ipld:
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5. Why BTCR is interesting
● Long-lived, recipient-owned EDU/OCC verifiable credentials
● “Subject” of credentials => the biggest challenge is identity
● User-friendly approaches to cryptographic key management lacking
● Risk to longevity and usability
● Solution is DIDs
● BTCR’s simplicity
● Bitcoin blockchain already available!
● Simple implementation, minimal feature set => easy to reason about
● Useful baseline from which to understand with more advanced DID capabilities
● Can start experimenting with DIDs immediately
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6. How it works
● An example BTCR DID
● Finding on the Bitcoin blockchain
● Creating
● Updating
● Resolving

7. A BTCR Decentralized Identifier
● References network (mainnet, testnet3, …), block height and position
● Bech32 encoded Transaction Position References
● Proposed extensions
● From this string, a BTCR DID resolver can generate a DID Document
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did:btcr:xkyt-fzgq-qq87-xnhn

8. Preview: BTCR DID Document
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More on this
later

9. Where it lives on the Bitcoin blockchain
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did:btcr:xxxx

10. Creating a BTCR DID
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11. Updating a BTCR DID
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12. Resolving a BTCR DID
● Build “implicit” DID from transaction
● Lookup continuation DID Document
● Build final “constructed” DID document
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13. Demos
● Resolving step-by-step
● Creating
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14. BTCR Resolver
Playground
https://weboftrustinfo.github.io/btcr-tx-playground.github.io/
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15. BTCR Resolution: Implicit DID Document
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● Derived Exclusively
from the Transaction
● Default
authentication
capability from
signing key
● “Continuation” DID
Document
● Method-specific
metadata

16. BTCR Resolution: Look up Continuation
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● “Continuation” DID Document Contents
● Immutable vs mutable storage and
signatures

17. BTCR Resolution: Constructed DID Document
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18. BTCR Creation
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19. Discussion
● Limitations
● What you can do with a BTCR
DID
● Other DID Method Specs and
capabilities
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20. Limitations and Quirks
● NodeJS libraries use
explorers
● Explorer vs Bitcoin node
● C++ libraries offer
more robust options
● Various quirks
● Confirmation time
● Continuation DID
Documents
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Issues: https://github.com/w3c-ccg/didm-btcr/issues

21. What you can do with a BTCR DID
● Sign a Verifiable Credential
● Authenticate (DID Auth)
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22. Other DID capabilities
● Guardian-managed
● m of n signatures
● “Social” recovery
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23. Get involved
● Incubate
● User stories
● Prototype
● Whitepapers
● Hackathons
● Blockchain Commons (Christopher Allen)
● Draft Specifications
● Contribute Use Cases
● Code and other specs
● BTCR: see references + Ryan Grant/Dan
Pape’s C++ repo
(https://github.com/dcdpr/btcr-DID-method)
● Method Specs
● DID Auth
● Resolver
Internet Identity Workshop Rebooting Web of Trust
Credentials Community Group
Decentralized Identity Foundation
• Credentials CG
• Verifiable Claims WG
• Veres One CG
• DID WG (soon)
SSIMeetup.org

24. References from this talk
● SSI Meetup Webinar Decentralized Identifiers (DIDs), Drummond Reed:
http://ssimeetup.org/decentralized-identifiers-did-fundamental-block-self-sovereign-identity-drummond-reed-webinar-2/
● DID Draft Specification: https://w3c-ccg.github.io/did-spec/
● DID Method Registry: https://w3c-ccg.github.io/did-method-registry/
● How BTCR resolution works, Kim H. Duffy, Christopher Allen, Ryan Grant, Dan Pape:
https://github.com/WebOfTrustInfo/rebooting-the-web-of-trust-spring2018/blob/master/final-documents/btcr-resolver.pdf
● Universal Resolver, Markus Sabadello: https://medium.com/decentralized-identity/a-universal-resolver-for-self-sovereign-identifiers-48e6b4a5cc3c
● BTCR Playground: https://weboftrustinfo.github.io/btcr-tx-playground.github.io/
● Related Libraries:
● https://github.com/WebOfTrustInfo/btcr-did-tools-js
● https://github.com/WebOfTrustInfo/txref-conversion-js
● Bech 32 Encoded Transaction Position References, Jonas Schnelli:
https://github.com/veleslavs/bips/blob/c83837536d6629f754ce5a88bbe245e0a615e76e/bip-XXXX-Bech32_Encoded_Transaction_Position_Referenc
es.mediawiki
● Summary of Proposed Extensions: https://github.com/w3c-ccg/didm-btcr/issues/1
● Proposal, Dan Pape: https://github.com/danpape/bips/blob/Bech32_Encoded_TxRef/bip-0136.mediawiki
● Blockcerts: https://www.blockcerts.org/
● Groups:
● W3C Credentials Community Group: https://www.w3.org/community/credentials/
● Internet Identity Workshop: https://www.internetidentityworkshop.com/
● Rebooting Web of Trust: http://www.weboftrust.info/
● Decentralized Identity Foundation: http://identity.foundation/
SSIMeetup.org

25. twitter.com/kimdhamilton
DIDs Demystified
A hands-on intro to DIDs via the BTCR DID Method
June 6, 2018
SSIMeetup.orghttps://creativecommons.org/licenses/by-sa/4.0/
Kim Hamilton Duffy
CTO of Learning Machine, Principal Architect of Blockcerts and co-chair W3C Credentials
Community Group