private&fast tx sidechains for any relay/parachain

[brenzi]

Motivation

Since a long time we have a working demo and potential product with our private tx demo sidechain

We could take this to a standalone product which could serve any other parachain or relaychain, even accross Kusama or Polkadot. Without the need of any changes to the target runtime we could shield the respective native token into the sidechain and unshield it back. The sidechain would just own and watch an account on the target chain and only simple balance transfers would be possible.

Advantages:

• We or anyone could deploy and operate sidechains for any para/relay chain as-is without our or the target chain's consent
• The entire dotsama ecosystem gets an L2 for balance transfers. private and low-latency
• The sidechain maintains a full reserve on L1. the total supply of the sidechain equals the balance of the sidechain account
• Later, an upgrade could include EVM/WASM smart contracts which would give private smart contracts to any target chain irrespective of L1 features.

Economics

For best UX, the native token of the sidechain would have to be the native token of the target L1 chain. tx fees would be paid in that token. Revenues could go to the operator of the validateer

The operators of the validateers need to pay fees in TEER on integritee parachain for RA and sidechain finality

Requirements

MVP

• make light client modular and optional #508

MLP

• make sidechain rpc compatible to polkadot-js/api and other dotsama wallets #1186
• Instead of customizing balance pallet index for each chain, we may want to rely on XCM exclusively to talk to the target chain. A new target chain would then be a matter of configuration, no code touched