Many upstreams possible

[mratsim]

AMCL repo contains the sources we were tracking. The current commit we track is quite old:

• https://github.com/apache/incubator-milagro-crypto-c/tree/fa0a45a35dfb0e6d16b5d4f9e0bca19b5460fe4b

Since then:

• It has been renamed from AMCL to incubator-milagro-crypto-c
• the original amcl repo the Apache Foundation forked (at https://github.com/miracl/amcl) is in maintenance mode
• the repo for new cryptographic development is now https://github.com/miracl/core (edit: ⚠ relicensed AGPL)
• It tracks the new BLS signature scheme standard https://github.com/miracl/core/commit/1e660e0bd6729b253089e66c8296a6223f9f1421
• Confusingly the Apache repo has a BLS SSS commit (https://github.com/apache/incubator-milagro-crypto-c/commit/db8d27d0cc9987bed2d0c9531d6fe605e8833bb4) but it stands for Shamir Secret Sharing and not Short Signature Scheme
• MIRACL/core also has RISC-V and Arduino support if it ever becomes of interest with benchmark and ultra low-power platforms: https://github.com/miracl/core/blob/master/MIRACL_Core.pdf

For action

Ultimately, the codebases are still pretty similar at the moment but we should expect them to diverge with time, including with bug fixes.

This means that it may make sense to reconsider using Apache as upstream and instead use MIRACL.

[mratsim]

The new Miracl/core is relicensed AGPL so we keep the Apache upstream.

TODO: update the submodule, it has been a couple months

[mratsim]

Solved by #66 and #68 and the preparatory work in https://notes.status.im/nim-bls-curve-backends