Unique docs

Account

There are two types of accounts in Unique Network:

  • Native substrate accounts. The generic substrate account looks like 5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY.
  • Ethereum accounts, a 42-character hexadecimal string starting with 0x.

Because of different formats, substrate and ethereum addresses cannot interact directly. For example, you cannot send tokens with Metamask to the Substrate address.

Account mirrors

Mirroring is a mechanism that allows you to get address representation in a different format—substrate for ethereum address and ethereum for substrate.

You can play around with the address converter in the reference section.

For example:

  • Ethereum mirror for 5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY is 0xd43593c715Fdd31c61141ABd04a99FD6822c8558. When a substrate account calls contracts, the msg.sender will be its mirror.
  • Substrate mirror for 0xd43593c715Fdd31c61141ABd04a99FD6822c8558 is 5FrLxJsyJ5x9n2rmxFwosFraxFCKcXZDngRLNectCn64UjtZ

WARNING

It is not possible to calculate the original account from the mirror account. This is a one-way mapping because of the different sizes between EVM and Substrate accounts.

Here are the primary use cases for mirrors

  1. If you want to send tokens from a substrate account to an ethereum account, send them to the latter's substrate mirror.

  2. The opposite operation works with one tradeoff. Tokens sent to the ethereum mirror of a substrate account will not directly top up the substrate account's balance. However, the substrate account can "withdraw" tokens from its ethereum mirror using the api.tx.evm.withdraw method.

The other question appears here. If the caller is a mirror, the beneficiary of a contract execution would also be the mirror, not the original Substrate address. For example, as a result of a swap on a DEX, all the tokens would be transferred to the mirror. How can this be solved?

Substrate account can transfer from its mirror

  • Native tokens, such as UNQ or OPL, can be withdrawn with evm::withdraw extrinsic
  • All native NFTs, Fungible, and ReFungible can be transferred using transferFrom.

However, this is not a great experience, so Unique provides a CrossAddress structure for Solidity.

Using CrossAddress

This struct represents an EVM or Substrate account in Solidity. It has two properties: sub for a Substrate account and eth for an EVM account. Only one property can be filled.

struct CrossAddress {
  address eth;
  uint256 sub;
}
  • For the EVM account, set the eth property with the EVM address (0x...), and the sub should be 0.
  • For the Substrate account, set the sub property with the substrate public key in the decimal format. The eth property should be equal to Ethereum zero address (0x000...00000);

Code example

To get an accounts mirror, use Address util from @unique-nft/utils.

import { Address } from "@unique-nft/utils";

const ethMirror = Address.mirror.substrateToEthereum('5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY');
// 0xd43593c715Fdd31c61141ABd04a99FD6822c8558

const subMirror = Address.mirror.ethereumToSubstrate('0x1B8EeEC6eD7e9C6B98291A8274c006e251902Ef3');
// 5FkhL2YH6rZD2AspxMBoUfFnA4GwWVKHVTbL1kChhYMvSq7B

The following articles will teach you more advanced concepts that make the developer and user experience smoother.