Compressed public key DID for NIST ECDSA curves

[dholms]

The multicodec spec says that the public key DID for NIST ECDSA should be the compressed public key (33 bytes) instead of the full (64 byte) public key.

https://github.com/multiformats/multicodec/blob/e9ecf587558964715054a0afcc01f7ace220952c/table.csv#L141

[dholms]

I'm planning to implement this btw 👍

Couple links:

• did:key discussion
• ceramic code around this same problem
• stack overflow the ceramic code is based on

[dholms]

Implemented internally here: https://github.com/bluesky-social/adx/pull/139/files#diff-c4ab40937a57e2f51e45e0e65f47c9a6d94a9e75b1f86ddf4f563f1c09028587R47

I ended up using big-integer.js because native BigInts don't have fully support & they don't support the necessary modular arithmetic & would require an extension anyway: bigint-mod-arith

Happy to pull this over & make a PR, just wanna know that we def want it here 👍

This also only implements it for NIST P-256 atm & not for the other NIST curves. Same logic though, just different curve params.

Thoughts? @matheus23

[matheus23]

Happy to pull this over & make a PR, just wanna know that we def want it here +1

This also only implements it for NIST P-256 atm & not for the other NIST curves. Same logic though, just different curve params.

Thoughts? @matheus23

Looks good! Would love to approve such a PR 👍