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Add Implementation Guidance to Recommend Compressed Point Encoding #117

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merged 8 commits into from
Feb 7, 2024
Merged

Add Implementation Guidance to Recommend Compressed Point Encoding #117

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725f230
Fix minor typo
frankhinek Feb 5, 2024
d1c7098
Add key representation guidance to use compressed point encoding
frankhinek Feb 5, 2024
768d73e
Rewrite summary for Representing Keys
frankhinek Feb 5, 2024
21131ba
Correct typo in example and use compressed point encoding
frankhinek Feb 5, 2024
4fa6241
Update spec latest update date
frankhinek Feb 5, 2024
6828d8d
Change compressed point encoding to MUST
frankhinek Feb 5, 2024
eb47b1e
Merge branch 'main' into spec-compressed-keys
decentralgabe Feb 7, 2024
361f26d
Make key representation guidance required
frankhinek Feb 7, 2024
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17 changes: 10 additions & 7 deletions spec/spec.md
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Expand Up @@ -9,7 +9,7 @@ The DID DHT Method Specification 1.0

**Draft Created:** October 20, 2023

**Latest Update:** January 26, 2024
**Latest Update:** February 5, 2024

**Editors:**
~ [Gabe Cohen](https://github.com/decentralgabe)
Expand Down Expand Up @@ -299,7 +299,7 @@ An example is as follows:
the zero-indexed positional index of the Service (e.g. `_s0`, `_s1`).
- Each [Service](https://www.w3.org/TR/did-core/#services)'s **data** is represented with the form `id=M;t=N;se=O`
where `M` is the Service's ID, `N` is the Service's Type and `O` is the Service's URI.
- Multiple service endpoints can be represented as an array (e.g. `id=dwn;t=DecentralizedWebNodes;se=https://dwn.org/dwn1,https://dwn.org/dwn2`)
- Multiple service endpoints can be represented as an array (e.g. `id=dwn;t=DecentralizedWebNode;se=https://dwn.org/dwn1,https://dwn.org/dwn2`)
- Additional properties ****MAY**** be present (e.g. `id=dwn;t=DecentralizedWebNode;se=https://dwn.org/dwn1;sig=1;enc=2`)

An example is given as follows:
Expand Down Expand Up @@ -380,8 +380,8 @@ A sample transformation of a fully-featured DID Document to a DNS packet is exem
| _did.TLD. | TXT | 7200 | v=0;vm=k0,k1;auth=k0,k1;asm=k0,k1;inv=k0;del=k0;srv=s1 |
| _cnt.did. | TXT | 7200 | did:example:abcd |
| _aka.did. | TXT | 7200 | did:example:efgh,did:example:ijkl |
| _k0._did. | TXT | 7200 | id=0;t=0;h=afdea69c63605863a68edea0ff7ff49dde0a96ce7e9249eb7780dd3d6f2ab5fc |
| _k1._did. | TXT | 7200 | id=HTsY9aMkoDomPBhGcUxSOGP40F-W4Q9XCJV1ab8anTQ;t=1;k=BCiNAz7y-XBr853PBAzgAOU_c0Hyw0Gb69Hr9jTC3MQ80iSbXxZo0jIFLtW8vVnoWd8tEzUV2o22BVc_IjVTIt8 |
| _k0._did. | TXT | 7200 | id=0;t=0;k=afdea69c63605863a68edea0ff7ff49dde0a96ce7e9249eb7780dd3d6f2ab5fc |
| _k1._did. | TXT | 7200 | id=HTsY9aMkoDomPBhGcUxSOGP40F-W4Q9XCJV1ab8anTQ;t=1;k=AyiNAz7y-XBr853PBAzgAOU_c0Hyw0Gb69Hr9jTC3MQ8 |
| _s0._did. | TXT | 7200 | id=dwn;t=DecentralizedWebNode;se=https://example.com/dwn1,https://example.com/dwn2 |

### Operations
Expand Down Expand Up @@ -778,13 +778,16 @@ encoding format, we recommend additional considerations to keep payload sizes mi

#### Representing Keys

Apart from the encoding of the cryptographic key itself, which cannot be further minimized in size, we ****RECOMMENDED****
the following representations of keys and their identifiers using `JsonWebKey`:
The following representations of keys and their identifiers using `JsonWebKey` (JWK) are ****RECOMMENDED****:
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- The [[ref:Identity Key]]'s identifier ****MUST**** always be `0`.
- Key identifiers (`kid`s) ****MAY**** be omitted. If omitted, upon reconstruction of a DID Document, the JWK `kid`
is set to its JWK Thumbprint [[spec:RFC7638]].
- DID Document representations ****SHOULD**** always use fully qualified identifiers (e.g. `did:dht:uodqi99wuzxsz6yx445zxkp8ddwj9q54ocbcg8yifsqru45x63kj#0` as opposed to `0` or `#0`)
- [[ref:DID Document]] representations of elliptic curve (EC) keys ****MUST**** include the x- and y-coordinate pair.
To conserve space in the DNS packet representation, compressed point encoding ****MUST**** be used to transmit the
x-coordinate and a sign bit for the y-coordinate. This practice reduces each public key's size from 65 to 33 bytes.
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is this true for all key types?

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@decentralgabe it is true for all EC key types. In terms of current key types in the DID DHT Registry, that includes secp256k1 and secp256r1.

It is not relevant for OKP keys such as Ed25519 since compressed encoding (only the 32-byte x-coordinate) is always used.

- [[ref:DID Document]] representations ****SHOULD**** always use fully qualified identifiers (e.g.
`did:dht:uodqi99wuzxsz6yx445zxkp8ddwj9q54ocbcg8yifsqru45x63kj#0` as opposed to `0` or `#0`)

#### Historical Key State

Expand Down
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