Re: Selective Redaction - docs and examples?

On Fri, Feb 21, 2025 at 7:23 AM Andrea D'Intino <andrea@dyne.org> wrote:

> writing live from CCG data-integrity meeting: does anyone has some and
> examples about "selective redaction" (maybe Calvin Cheng?)
>
The term **"selective redaction"** lacks a well-defined formal meaning,
though it has gained traction—particularly within the Singapore DID/VC
community—to describe specific hash-based redaction techniques in
credential verification. However, at Blockchain Commons, we have generally
preferred the term **"elision"**, as the underlying technique is useful for
more than just redaction.

The earliest reference to this topic within the W3C community that I’m
aware of is from 2016:

   Redaction Signature Suite 2016:
https://w3c-ccg.github.io/lds-redaction2016/

This JSON-LD Signature Suite used a hash list approach, but I don't know if
it was ever formally implemented. I believe the Singapore DID/VC community
uses something similar to it. ISO mID/mDOC also uses a hash list approach,
but they don't call it selective redaction.

Elision, as we define it at Blockchain Commons, enables **structured
omission** of data while preserving cryptographic integrity. This allows
verifiable claims to be **selectively revealed or concealed** without
invalidating proofs. Unlike redaction, which focuses on removing data,
**elision can support progressive disclosure, controlled compression, and
layered encryption**, making it applicable to a wider range of use cases.

We avoided the term **"selective redaction"** due to potential confusion
with **"selective disclosure."** Historically, selective disclosure
referred to **minimal disclosure**—revealing only the necessary subset of
data. However, more recently, it has also come to describe cryptographic
techniques like **BBS proofs**, which focus on unlinkability and
anti-correlation of signatures. Given these evolving meanings, precision in
terminology is crucial.

For those interested, I’ve written extensively on **selective disclosure
and data minimization** in the context of verifiable data exchange:

    Musings of a Trust Architect -- Data Minimization & Selective
Disclosure:
https://www.blockchaincommons.com/musings/musings-data-minimization/)

We have useful section of a our video on Gordian Envelope specifically
about "Elision and Redaction" starting at the 6m25s mark:

    Understanding Gordian Envelope (#Elision and Redaction 6m25s):
https://youtu.be/-vcLCFKQvik?feature=shared&t=385

On Fri, Feb 21, 2025 at 3:39 PM Steve Capell <steve.capell@gmail.com> wrote:

> The “selective redaction” that is needed for supply chain use cases has a
> similar sounding name but very different use case
>
> It’s not the subject / holder of the credential that wants to redact in
> supply chain - it’s the verifier that needs to redact it before passing it
> on to the next actor
> - personal use case : I want to redact MY personal details in MY
> credential before I show it to a verifier that wants it
> - supply chain use case : I received a credential from my supplier
> containing claims about my supplier (eg my farm is deforestation free).  I
> need to redact the supplier name before I pass it on to my customer as
> evidence that my product is made from deforestation free inputs
>
> Sounds similar - but big difference in how it could be implemented.  This
> supply chain use case is the rationale behind the trade trust (Singapore)
> selective redaction proof method
>

For those interested in other practical use cases of elision (or "selective
redaction"), we written about how it can be applied across industries such
as education, where it enables secure, selective sharing of student
records; wellness, where it protects sensitive health data while supporting
controlled disclosures; and data distribution, where it ensures recipients
only access necessary information. More details can be found here:

    Envelope Use Cases Overview:
https://developer.blockchaincommons.com/envelope/use-cases/

For more details on our specific **elision and our specific implementation
within Gordian Envelope**, which uses structure hash trees, see:

    Envelope Developer Overview:
https://developer.blockchaincommons.com/envelope/
    IETF draft-mcnally-envelope-08 -- The Gordian Envelope Structured Data
Format: https://datatracker.ietf.org/doc/draft-mcnally-envelope/

I’d be happy to provide additional pointers or discuss further if anyone is
interested.

-- Christopher Allen