SIP: 20

 Layer: Core

 Title: The Validation Matrix

 Author: Brian Burrell 

 Comments-Summary: No comments yet.


 Status: Final

 Type: Standards Track

 Created: 2018-10-13

 License: PD

This SIP describes the specific usage of the Matrix extended transaction type for the purposes of blockchain validation with the ShionCoin scripting system.

The purpose of the Validation Matrix is two-fold; one purpose is to provide an additional redudant mechanism to ensure the blockchain's validitity, and second to supply a method for a consensus of nodes to generate a dynamic checkpoint on the blockchain.

Every 27 blocks a "validation matrix" is required to be generated on the block-chain in the case where there are no other transactions in the block being submitted other than the coinbase. The matrix is encapsulated in the coinbase using a matrix extended transaction, and has a coin output of one coin. The other-wise total reward of the coinbase is reduced by a single coin.

The numeric information in the "validation matrix" is composed of a running hash split into 9 cells which is directly based on the preceeding block-chain. The validation matrix acts as a redundant security measure in order to ensure that the block-chain is viewed in a consistent manner between all nodes. Note that the validation matrix does not provide in itself anything more than an additional checksum mechanism to the existing block-chain.

In addition to providing a supplemental level of integrity to the block-chain in the form of a "redundant merkle hash", the validation matrix is also used to initiate a sequence of events that potentially lead to a new dynamic checkpoint being established. This is performed by a consensus vote led by active partipants (referred to as notaries) on the block-chain.

Each node which generates a "validation matrix" becomes a candidate to become a "notary". When enough notaries are available the validation matrix which use a multi-sig output which contains the pubkeys from all participating notary nodes.

A "notary transaction" has a single input; the latest validation matrix transaction. It is signed by each node (in order) until the transaction is finalized and complete. Once, and if, completed, a dynamic checkpoint will be made for the block which contained the "validation matrix" transaction. Note that only the last validation matrix block on the block-chain will be considered as a potential checkpoint.

The output of the notary transaction is a "null return" which will result in the original coin being transformed back into a claimable miner transaction fee (less a small amount for additional ensued transaction fees).

Dynamic Checkpoints
Dynamic checkpoints, in essence, are similar to the delayed proof-of-work (dPOW) concept. The dynamic checkpoints are intended as a way to provide resiliance, and therefore extra security, for the integrity of the block-chain. By providing additional "agreed upon" checkpoints dynamically it becomes more difficult to maliciously alter or otherwise by performing a "51% attack".

The output of a validation matrix coinbase transaction can either be OP_RETURN or a multi-sig redeem script which includes a minimum consensus of notary pubkey addresses.

Here is an example of a notary transaction:



	"vin":[{"txid":"2788f12789b27c9167b56a34c696dc117bb5939d00b70a3474aae451cbed3962","vout":0,"scriptSig":"0 3045022100bba304fb584f1ace2f101fd7ada1d36475da8f3ad9178e99029a020614e3208202204e9ae644ea6a6d5d184097f4ce4ba6a17cf92201936aa37d15637f8ee32d0fd601","sequence":4294967295}],



An incomplete "notary tx" is submitted and each node with a public signature included in the transaction's multi-sig redeem script will sign the transaction, and then submit it again. This is done in the order of the pubkeys listed in the multi-sig redeem script.

At no point will a incomplete "notary tx" be added to the transaction memory pool and the "input sequence" to a non-final value until all signatures have been squired. Nodes which do not have a public key address listed in the multi-sig redeem script will still relay the transaction even if it's incomplete. In order to avoid redundancy, a node will only sign the "notary tx" if it's own public is the next in line that has not been signed pertaining to the multi-sig pubkey order.

At this point, a new checkpoint will be established for the block containing the validate matrix transaction providing the following three criteria are met:

  1. The "notary tx" references the latest Validation Matrix established,
  2. the "notary tx" has a single input containing a Validation Matrix transaction, and
  3. the "notary tx" has a single output OP_RETURN and a coin value of zero (0).

This document is placed in the public domain.