new section §1.2

Author: shannona

docs/01_2_Core_Concepts.md

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+# 1.2: Understanding Core Concepts
+
+Self-sovereign identity tells the core story of XIDs: why they exist
+and what they do. However, XIDs are built on a number of additional
+core concepts. They're all detailed in the [Core Concepts
+documents](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/README.md)
+and further summarized here.
+
+All of the core concepts are useful for understanding XIDs, but you
+may particularly want to read the discussions of [Data
+Minimization](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/data-minimization.md)
+and the technologies for
+[XIDs](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/xid.md)
+and [Gordian
+Envelope](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/gordian-envelope.md).
+
+## Core Philosophies
+
+[**Attestation & Endorsement
+Model**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/attestation-endorsement-model.md). An
+attestation is a formal statement of something. Broadly, it can come
+in two forms: a self-attestation, which is a formal statement you make
+about yourself, and a peer endorsement, which is a formal statement
+that you make about something else. Attestations and endorsements are
+closely related to claims and credentials in the larger world of
+identity.
+
+An attestation is most powerful if it's provable, partially or
+fully. Building out context for an attestation can also help in
+that. Beyond that, the value of an attestation ultimately depends on
+the reputation of the person making the attestation. Your
+self-attestations, beyond what can be proven, are only as strong as
+your reputation. Your peer endorsements ultimately lend your
+reputation to the people your endorse: if they prove incorrect, your
+reputation suffers.
+
+[**Data
+Minimization**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/data-minimization.md). The
+concept behind data minimization is simple: you should disclose the
+minimal amount of data that you need to at any time. Making an
+age-restricted purchase is the traditional example: you shouldn't have
+to show your driver's license, which has lots of other personal
+information about you, you shouldn't even have to reveal your age,
+simply that your age is within the range that allows the purchase.
+
+This isn't a philosophical question of privacy. Every bit of
+information that you reveal is dangerous. It might allow correlation,
+revealing something more than you intended. It might be used for
+purposes that you didn't intend. It might create possibilities for
+coercion. It might cause prejudice or disadvantage. And every bit of
+data that you reveal is potentially out there forever.
+
+[**Elision
+Cryptography**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/elision-cryptography.md). One
+way to support _Data Minimization_ is to selectively elide (remove)
+information from documents before you send them out, ensuring that
+what you send to each person only contains the information that you
+need to know.
+
+Crypographic elision takes the next step: it preserves hashes of
+elided data so that you can later prove that the data was in a
+document, even after it is removed. If signatures are made across data
+hashes, rather than the data itself, then the signatures also remain
+valid. This allows for the creation of signed credentials that the
+credential holder can selectively elide to ensure _Data Minimization_.
+
+[**The Fair Witness
+Approach**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/fair-witness.md).
+Another way to increase the value of _Endorsements_ and other
+_Attestation_ is by using the fair witness approach: you carefully
+attest to only what you can independently determine, you acknowledge
+any biases in the observation, you add context that's important to the
+observation, and you document it all as part of the _Attestation_.
+
+Even if a fair-witness _Attestation_ reveals bias, it can still be
+more valuable than an _Attestation_ without that contextual
+information, because it allows the reader of the _Attestation_ to better
+assess what it actually means.
+
+[**Key
+Management**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/key-management.md). Keys
+are what make the trustless world of cryptographic identities and
+digital assets go 'round. They're what control your identity and
+assets, and what you use to prove ownership of the same. Without the
+keys, you literally have nothing.
+
+Key management is what ensures you maintain control of those
+things. Its built on a foundation of heterogeneity, meaning that you
+use different keys for different things, so that when you lose one,
+you don't lose everything. Beyond that, it requires key rotation and
+revocation as things change over time.
+
+[**The Progressive Trust Life
+Cycle](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/progressive-trust.md). In
+real life, trust is a progressive thing. When you meet someone and
+grow your relationship over years, you slowly extend new information
+to them, slowly learn new things about them, and so over time gain
+increasing trust of them (or possibly the opposite, depending on what
+you learn).
+
+The progressive trust life cycle models real-world relationships as a life
+cycle of increased disclosure and trust. It's intended as a foundation
+for how digital relationships can be similarly modeled, in part by
+using the concept of _Data Minimization_. This replaces the
+all-or-nothing disclosure that is much more common on the 'net today.
+
+[**Pseudonymous Trust
+Building**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/pseudonymous-trust-building.md). Revealing
+your identity can be dangerous. This has become very obvious in recent
+years when judges, politicians, and other people impacting the civil
+society of America have been targeted and even killed for what they
+said or did. One solution is to adopt a pseudonymous identity: a
+stable identity that is not associated with your real-world self.
+
+The problem with pseudonymous identities is creating trust for
+them. However, that trust can be bootstrapped through a _Progressive
+Trust Life Cycle_ that includes quality work, verifiable
+self-attestations, and contextual peer endorsements. Over time, a
+pseudonymous identity can gain as much trust as a real-world identity.
+
+[**Public Participation
+Profiles**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/public-participation-profiles.md). Public
+participation profiles are _Pseudonymous_ identities that are created
+specifically so that the identity holder can engage in public
+projects.
+
+There are risks to participation, as they can expose information that
+you hadn't intended, and managing your pseudonymous identity requires
+all of the care of any _Pseudonymous_ identity. But there can also be
+rewards in good work done.
+
+## Core Technologies
+
+[**Gordian
+Envelope**](https://github.com/BlockchainCommons/XID-Quickstart/blob/main/concepts/gordian-envelope.md). The
+Gordian Envelope is a "smart document" system that collects and
+displays data in a regularized, deterministic way. Its recursive
+design allows for the storage of great depths of information, while
+its self-describing foundation ensures that it's always possible to
+see what a Gordian Envelope is and what it contains.
+
+One of the greatest strengths of Gordian Envelope is its use of
+_Elision Cryptopgraphy_. The holder of an envelope can practice _Data
+Minimization_ by eliding any information in an envelope while
+maintaining any signatures on the envelope and any credentials it
+might hold.
+
+[**XID**](xid.md). Obviously this whole course is about XIDs,
+Blockchain Commons' self-sovereign identifier. The XID core concept
+document briefly outlines what a XID is, what it contains, and how
+it's created.
+
+XIDs are built on _Gordian Envelope_ using a tight structure that
+limits what objects can be placed at the top level of an envelope to
+standardize and simplify their content.
+
+## Summary: Getting to the Core
+
+Why XIDs? These core concepts explain some of the reasons:
+
+_ They enable _Pseudonymous Trust Building_ where you can build up a pseudonymous identity over time, including _Public Participant Profiles_ for working on public projects.
+- They allow for _Attestations_ and _Endorsements_ to be attached to your identity, possibly using a _Fair Witness Approach that will improve their trustworthiness.
+- They support _Data Minimization_ using  _Elision Cryptography_ ensures that allows the holder to decide what to reveal while ensuring that signed statements remain valid.
+- This allows a _Progressive Trust Life Cycle_ where you reveal details over time, just like in the real world.
+- They support _Key Management_ that enables the best practices of heterogeneity and rotation.
+
+## What's Next
+
+You're now ready to begin [§1.3: Creating Your First
+XID](01_3_Your_First_XID.md), to get your hands into the actual work
+of XIDs.