This is a proposed decentralized bridge for $BCH <=> $SBCH.
Did you know? SHA-Gate stands for "Smart-Holder-Authorized Gate".
The first version was published to the SmartBCH public GitHub repo on Aug 17, 2021. In addition to all of the contract source code is a complete, step-by-step Testing Guide.
GitHub - smartbch/shagate: smartBCH SHA-Gate
SHA-Gate Version 1
The 2nd version of SHA-Gate has already been propsed by the SmartBCH team, with notable improvements to private key storage.
The Plan for SHA-Gate V2
SHA-Gate Version 2

SHA-Gate v1 is available to test on Testnet, following the instruction here.
shagate/ at main · smartbch/shagate
SHA-Gate v1 Testing Guide
Unfortunately, we do not yet have a public source available for v2.

There has been no "official" release date set for SHA-Gate to be deployed to production.

Besides the delays in release, which have lead to much discontentment throughout the SmartBCH community, there have been a number of criticisms raised about the effectiveness of the current proposition.

This number is assumed to still be THREE (3).

Version 2 suggests the use of 2nd-layer of protection in the form of "Monitors". These monitors will have the power to block any transaction that is deemed to violate the agreed rules of the contract. As in the event of a hacker overtaking control of one of the Validators.
It has been suggested that this Monitoring layer is redundant.

The current SHA-Gate Treasury is being held here

MathieuG has proposed several upgrades to the SHA-Gate, both v1 and v2, that introduce several improvements over the work proposed by the SmartBCH team.
GitHub - mr-zwets/upgraded-SHA-gate

  1. 1.
    With new architecture miners need to vote one time each coinbase at most.
  2. 2.
    New architecture allows users to bridge to SBCH with minimal trust.
  3. 3.
    Upgraded contract uses fixed length voting period to enforce voting window.
  4. 4.
    New architecture gets rid of the need to signal for which SHA-gate you want to vote for, uniqueness of one vote per coinbase can be required by restricting voting vout to a certain index.
  5. 5.
    Changed initializing a proposal to be done by m-of-n operators, can fit 5-of-7 for example.

In addition to open-sourcing the code, MathieuG has prepared a LIVE working demo for his upgrades found here.
Demo decentralized bridge
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Production Release
Number of validators
Security monitors
Upgraded SHA-Gate
Benefits & Highlights
Working Demo