Transcript By: Bryan Bishop
The topic that we have been working on is identity for everyone. In terms of trusted set of parties if you will, that can potentially provide some level of attestation to the identity and that can be provided in a digitized manner as to what levels of service an be provided to that level of identity as well.
What belongs in a blockchain? What works in a blockchain? What doesn’t work in a blockchain? How should it be stored? How can we make sure that there’s redundancy? What systems are reliable? Should we use cloud providers, or distributed hash tables, should we put certain data in the blockchain, we talked about zone files of the existing domain name system and how they can be used to have pointers to data store anywhere on the web. We talked about how in the blockchain you might want to associate a set of public keys with a domain name, and associate it with a hash of data where the data might be stored elsewhere. We brought up how, where hardware devices, we brought up the challenges of private key storage and protecting private keys. We brought up what happens when there’s some kind of key-compromise and how we can recover from that scenario. We talked about insuring that people can use multiple identities in multiple contexts, being able to preserve their privacy, being able to minimize data that they convey when they interact with someone else or some other application. I did we believe have a consensus on the fact that as little as possible should be stored in the blockchain. The blockchain should be used for very key use-cases, like associating a public key with a globally unique name with a hash of data. Everything else could be done off or outside the blockchain. You can cram things into the blockchain, depending on your use case, but if you identify that as the common minimum core then that clarifies and informs how someone would design and implement a blockchain-based identity system. What would be the next step? I believe the next step would be for people to, for everyone to come together and decide on some architectural standard around, like we agree on these principles and these ways on organizing information on the appropriate roles for the blockchain and cloud storage and everything else and agreeing upon standards like using DNS zone files. And hashing those zone files and putting those hashes on the blockchain. Use the existing standard of DNS zone files, and the existing format, for encoding pointers to data stored elsewhere. Things like that, agreeing upon the standards of those components in the different layers of the public key cryptographic identity naming and contextual identity layers.
Verifiable claims data model. We did not spend that much time talking about it. We talked about some interesting requirements and concerns. The idea is whether the idenitty has the right to reveal and conceal information about themselves. Selective disclosure came up a couple of times. Privacy was a big concern. Different actors have different requirements. Issuers of a verifiable claim is going to want to be able to revoke and edit claims over time. Whereas the receiver of the verifiable claim will need to be able to store it for a long time. There was some discussion regarding trying to … the current legal framework, can we take it and make verifiable claims happen that way? There was some healthy debate in our group. There was an assertion that we don’t need to standardize verifiable claims. That the problem is elsewhere. That blockchain is not a panacea. That was said a number of times. Folks wanted to know about the economic incentives of building identity systems. Are these aligned iwth the people going to be using it? What are the lifetimes of verifiable claims? How long do you have a right to be forgotten effectively? I think the group is good about not delving into the perma threads. What is an identity? What composes an identity? Even the statement where we said a set of attributes makes up an identity, was controversial. I think we avoided usual pitfalls. I don’t know if we came to any conclusion. More discussion is good.
What are the next steps? A number of folks are going to join the verifiable claims task force at W3C. That’s where you can learn some more about this work. And that’s kind of the first step in participating if you’re interested in expressing, transmitting or verifying verifiable claims.
What was controversial about the identity being a bundle of attributes? Ship of theseus. You can show how something can have 100% change in its attributes over time, and have literally zero attributes from the original ship. The only thing is persistence. So bundling attributes can be a problematic way to define identity.
Efficient thin client verification of identity
We discussed about efficient thin client verification of identity. Given a username, what is the set of public keys associated with that username? How can a thin client get this set securely and correctly? And how can we do this on a system like bitcoin? The assumption is that the client has all the blockhashes but not the block content. I would still like to get the set of public keys. I would like to do so efficiently without downloading the whole blockchain. There’s work on this like blockstack, namecoin, onename, and others. You collect all the blocks then query the state. The first problem is the non-membership proof problem. Blockstack has a merkle root for the entire state of the system. You can show that a particular operation belongs in the set. There is also a lite client proof system. A thin client cannot give a non-membership proof for the root. That’s the non-membership problem. The other problem is the freshness problem. On the non-membership problem, there might be some solutions like in ethereum where you index the data in your blockchain and you commit the index as a patricia tree or sorted merkle tree. Another way is using a linear commitment chain.
Once you have a patricia tree merkle root in the block header, you still need to know what is the most recent blockhash. There is roughly three ways to do it. The first one is with proof-of-work. You want to get the current blockhash. You want to get 6 confirmations of blockhashes to know that it is confirmed. Or you can query a lot of people for a blockchain hash chains and see okay this is the longest one, in this case that’s the longest answer for like six blocks away. Another way is a classical BFT system like tendermint is doing. In that case you can get an answer about what the most recent blockhash is. The third way is with an oracle system, like to commit collateral on the chain and if somehow they cna be enforced to only sign correct blockhashes or else they get their collateral slashed, then perhaps that’s the only way to get an answer with a guarantee.
Lastly there is something about out-of-band broadcast. Perhaps you might trust satellites to give you the correct blockhash. There’s two things to consider. There’s the non-membership problem like in patricia trees. Then there’s the recency problem with proof-of-work, BFT or oracles.
Next steps? Tendermint should specify its lite client protocol.
I would say that our super short summary is “too much identity”. We took a different view. Identity is not good. This is something we’re trying to avoid in many of these systems coming from bitcoin and other projects. Identity is a powerful tool. You can do a lot with it. We should have standards where you want the least possible amount of identity. Only rely on identity when you have gone through the other options. We already think there’s too much identity, unique identifiers, tracking, etc. Hopefully we can get rid of that with some of this.
You might have a spectrum of identities where you have total anonymity, or ephemeral key pairs where there are session key pairs perhaps, and then longer persistent identities that might be linked to a legal or biological entity. We think best practice would be to use the weakest and least powerful identity system. Use attribution. Use a set inclusion proof instead of a unique identity.
If you go to the taco truck and order a chicken taco, if they ask me for my name, I often give a fake name. They don’t care what your name is, they just need a unique identifier. This is an ephemeral session token. It does not need to be linked to a legal identity. That’s one aspect.
Another attribution aspect is that, say in the future there’s a taco drone delivery service using a darknet market or something. I want an inclusion proof that the FDA or taco inspectors have inspected the taco facility. But I don’t need to know who’s making the taco. All I need to know is that it has been inspected correctly. Use attribution when it suffices. Use ephemeral identities when possible. Use one that is not linked to a legal or biological identity.
Have repudiation when possible. Don’t sign, use diffie-hellman. Have something where it can be deniable afterwards by parties. Data is a liability. You don’t want lots of customer data. You don’t want lots of user data. You want to minimize this to the extent possible.
Next steps? We should have a best practices or sort of strive to work on this when making applications in the web space or blockchain space.
How does this relate if at all to persistent pseudonymous identities? That’s a fairly powerful identity which can still be unlinked to your legal identity. A lot of bitcoin is based on pseudonyms where we don’t know who it is, but we see a persistent entity. Having an ephemeeral identity discarded after each use is safer in many ways. Once you link a pseudonym to an actual person, you can go back and figure out everything. You don’t have forward secrecy in that scenario.
They have proposed an architecture for hyperledger based on IBM membership services. It’s a combination of centralized and decentralized services. They use the certificate authority nomenclature and structure as a way to build this service out. It’s a system built with the idea of long-term identity pieces and short-term identity pieces. When you are first creating or setting up on the blockchain, actually this gives a good reason to step back for a second. They built this proposal with the idea of private or permissioned ledgers in mind. Some of the things you will hear me talk about, may be more relevant in the private case than the public case. They have this idea of long-lived certs, called authorization certs. This gets generated when you’re creating an account or signing on to the blockchain for the first time. Then the idea of transactional certs where the transactions might have subset of attributes on it, and only used on a single transaction. The purpose of transactional certs is to help reduce and prevent correlation so that if someone is involved in one transaction can’t necessarily see the other transactions you’re involved in. One of the ideas was building something for the first authorization, you might be looking for a generic attribute, like “this person is a licensed plumber”. When they come back, you want to know that it’s the same person coming back. Specificity might go down over time in terms of who you’re dealing with. We’re heavily dependent on third-party validators in terms of our certificate authority structure. If your counterparty is taking any risk in th etransaction, they might want to have someone other than you who has signed off on your attributes. That was a lot of the high-level pieces that came in.