Pedersen commitments

[loongy]

Description

Pedersen commitments are introduced to enforce correct computations between the Darknodes.

Motivation

This prevents Byzantine Darknodes from producing false negatives. Previously, the system could only prevent false positives by slashing bonds when a bad confirmation was detected.

Design

The Blinding exponents are added to the shamir package, along with the Commitment object with a basic constructor.

The Fragment object in the order package uses a Blinding exponent to obfuscate its own shamir.Shares and also stores a set of Commitments for other fragments. These values are used by the smpc package and ome package to verify shares that are embedded in smpc.Join objects.

The verification process happens inside the smpc package.

Packages modified:

• shamir introduces the new Pedersen structures
• order uses the new Pedersen structures within the order fragments
• smpc introduces new fields to the Join object for storing Pedersen structures and implements the verification logic
• ome extracts the Pedersen structures from the order fragments and sends them to the smpc
• grpc is updated to support the new order fragment layout

Unresolved Issues

Tokens are not verified in this PR, nor is the functionality to check off-chain for false positives.

[coveralls]

Pull Request Test Coverage Report for Build 3392

• 85 of 313 (27.16%) changed or added relevant lines in 11 files are covered.
• 208 unchanged lines in 4 files lost coverage.
• Overall coverage decreased (-4.8%) to 68.41%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
orderbook/sync.go	0	1	0.0%
ome/matcher.go	31	32	96.88%
order/fragment.go	10	16	62.5%
smpc/message.go	0	13	0.0%
grpc/orderbook.go	14	32	43.75%
smpc/joiner.go	6	26	23.08%
shamir/shamir.go	1	44	2.27%
smpc/network.go	0	45	0.0%
smpc/smpc.go	0	81	0.0%

Files with Coverage Reduction	New Missed Lines	%
swarm/swarm.go	1	75.55%
smpc/message.go	22	31.78%
smpc/smpc.go	80	0.0%
smpc/network.go	105	0.0%

Totals
Change from base Build 3380:	-4.8%
Covered Lines:	4695
Relevant Lines:	6863

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💛 - Coveralls

[tok-kkk]

Merge round-robin-scheduling branch into pedersen-commitments branch