Trust:Security and its many mechanisms are used to establish trust; once trust is established, you just trust. My canonical use-case for this is access to the school blog. I can grant or revoke write access to my kids' school blog. I give access to people who I trust will only post age appropriate material. I could use manual or automated mechanisms to check posts before they are published but the effort or cost outweighs the risks. I choose to trust. Trust is a human, emotional, social construct that implies a loosening of control. Trust can be and it is, knowing the risks, the rewards and the remediations for abuse of trust is important (systems of accountability; reputation? legal?). So trust needs to be bounded "I trust XX to do YY".
Concretely: I trust an entity with my money, like coinbase, who has my bitcoin wallet. I have taken a leap. Coinbase could steal my money despite all of the controls of the blockchain and distributed ledger technology. I could use a different wallet technology but then I am still choosing to trust the software that enables that wallet, or the hardware that the software runs on. At some point the cost of not trusting outweighs the risk and the expense of trusting.
So on some level... this poses the question: If my relationship with coinbase is purely one of trust that they will hold my money and return it based on the current value of bitcoin, what difference does the underlying blockchain technology actually make to me? I could use bitcoin in a way that I don't need a trusted third party (at the extreme: build my own hardware and software) but I don't, and most people don't.
I think it is incumbent on people talking about identity systems to really understand where security ends and trust starts. Do most people understand how misplaced their trust in their mobile hardware could be?
So to me Trust is what happens beyond the bounds of control. Or to put it another way; Trust is what happens within 'pipes' or 'bubbles' of control established using security mechanisms.
Confidence:Confidence is, when I'm trying to use it precisely, a measure of certainty in a claim. In terms of an identity system a claim might be:
- an authentication claim (I am the person identified by ID XX)
- an authorization claim (I should have access to this resource)
- an attribute claim (I am over 18 years of age)
In an authentication claim, the claim of the ID may be accompanied with claims of who established the ID (signed by a private key of a trusted party) the claim may also include details of how the user was authenticated (password, multi-factor, smart card, etc...). The associated metadata establishes a level of confidence in the claim. Step-up authentication models (you can view your balance if you logged in with a password but you have to use multi-factor to initiate a transfer) are a direct result of your levels of confidence in various authentication claims.
In an attributes claim again one would expect the claim to be signed by a trusted party, trusted to make the specific claim, and the claim may include metadata about how the attribute was validated. An over 18 years of age claim that was self asserted (they checked a checkbox that says "i'm over 18") may be enough to satisfy COPPA compliance requirements in the US but would be insufficient to provide legal access to porn in the UK.
Bringing Confidence and Trust together:So with a claim that is signed by a party that is trusted to make age claims; the signature gives me confidence that claim is from the the trusted party and then I trust the age claim rarely do I require proof of the mechanics of acquiring the validation. Even if I require details of how the claim was was established (self asserted or credit system check) I could, but I don't, make the third party 'prove' it.
That is establishing a Trust space using a security mechanism (in this case; PKI and standardized claim semantics) and then... trusting the information that is provided in that secured context.