staking: allocate use channel public key

[abarmat]

• When allocating stake to subgraph the index node now must send the public key used in the payment channel.
• Allocate() advertises the public key in the AllocationCreated event so we can capture in our Network Subgraph, using that information consumers can route payments to the index node.
• Allocate() calculates the signer address of the index node in the payment channel by getting the Ethereum address from the public key.
• The signer address is used, as before, as one of the parties in the channel multisig and is validated to avoid reuse.

NOTE:

• This implementation uses a feature from Solidity 0.6 called array slices. https://solidity.readthedocs.io/en/v0.6.0/types.html#array-slices
• The linter and prettier still don't handle well that syntax.

Reported issues to both projects:

• Syntax error when using array slice on a bytes datatype duaraghav8/Ethlint#284
• IndexRangeAccess error when contract uses Solidity 0.6 calldata array slicing prettier-solidity/prettier-plugin-solidity#269

[Jannis]

Did you manage to verify that this is correct?

Two examples:
Public key 0x03a74c72b51f4d36e9e4a13616dddeae31bafe41b1662804476a6859e26d9c734f
Results in address: 0xcFFAc3084674cc596F1F91c16f8FBc2De16B3DC8

Public key 0x036b7b0e7896e59a8b9e0a940e25d253b18a25fefba08da3eeb19a25839ba65eea
Results in address: 0x72b7e00027212AEEe61B88d6aE714f278220b595

[Jannis]

I've verified that we can go from the public key to the Connext channel identifier, so I can confirm that channelID / signer address and public key are all I need.

[abarmat]

Yes, I verified it is working on the tests in test/staking/general.test.js

I used:

• Public Key '0x0456708870bfd5d8fc956fe33285dcf59b075cd7a25a21ee00834e480d3754bcda180e670145a290bb4bebca8e105ea7776a7b39e16c4df7d4d1083260c6f05d53'
• Address: '0x6367E9dD7641e0fF221740b57B8C730031d72530'

@Jannis note that the public key is in uncompressed format for Solidity to easily convert to address

Snippet on how to do that:

const publicKey = '0x026655feed4d214c261e0a6b554395596f1f1476a77d999560e5a8df9b8a1a3515';
let compressedPublicKey = ethers.utils.computePublicKey(publicKey, true);
let uncompressedPublicKey = ethers.utils.computePublicKey(publicKey, false);

console.log(compressedPublicKey);
// "0x026655feed4d214c261e0a6b554395596f1f1476a77d999560e5a8df9b8a1a3515"

console.log(uncompressedPublicKey);
// "0x046655feed4d214c261e0a6b554395596f1f1476a77d999560e5a8df9b8a1a35" +
//   "15217e88dd05e938efdd71b2cce322bf01da96cd42087b236e8f5043157a9c068e"

[abarmat]

@Jannis let me know if you are ok with the response so we can merge

[Jannis]

I wonder if this key here is an extended public key? It's much longer than a regular public key.

[abarmat]

I've just see this comment and posted an explanation in the comment before.

It's called uncompressed public key format. I posted a snippet using the ethers library on how to convert from one public key format to the other.

[abarmat]

I committed just one more change to bump to the newest version of solidity-prettier. They fixed the issue I reported.

[davekaj]

LGTM, i made one small note on a comment

[davekaj]

Only can => Can only

[abarmat]

Fixed and rebased!