# E-Money token project

An e-money, bank and central bank money issued token based on [ERC-20](https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md). With additional functionalities such as holds, clearance and detailed compliance.

This project is the first implementation of electronic money on a Blockchain. The learnings that were made during its creation were used to propose [ERC-2020 - The E-Money Token Standard](https://emoneytokenstandard.org/). Currently, there are differences between the interfaces used here and the proposed standard. The interfaces of the standard will be adapted in a future release.

Additionally, to the ERC-2020 standard the token allows cross ledger transfer. This means transferring tokens from one wallet in one blokchain network to another one in a different blockchain network

## Installation

The contracts and the corresponding build files can be downloaded with:

```
npm install emoney-token --only=production
```

## Interacting with the token

The abstract contract [EmoneyToken](contracts/EmoneyToken.sol) can be used to interact with the token. It consists of the following interfaces:

### ERC-20

Please refer to the [ERC-20 Token Standard](https://eips.ethereum.org/EIPS/eip-20) for the exact specification.

### Hold

An extension to the ERC-20 standard token which allows tokens to be put on hold. This guarantees a future transfer and makes the held tokens unavailable for transfer in the meantime. Holds are similar to escrows in that are firm and lead to final settlement.

Please refer to [IHoldable.sol](contracts/IHoldable.sol) for the exact specification.

#### balanceOf

The standard implementation of ERC-20 has been changed in order to deduct the held balance from the ERC-20 balance.

#### transfer

The standard implementation of ERC-20 has been changed in order to deduct the held balance from the ERC-20 balance. Any amount that is held cannot be transferred.

#### transferFrom

The standard implementation of ERC-20 has been changed in order to deduct the held balance from the ERC-20 balance. Any amount that is held cannot be transferred.

### Two Step Transfer (Clearable Transfer)

> "In banking and finance, clearing denotes all activities from the time a commitment is made for a transaction until it is settled." [[1]][Clearing-Wikipedia] 

Please refer to [ITwoStepTransferableToken.sol](contracts/ITwoStepTransferableToken.sol) for the exact specification.

[1] https://en.wikipedia.org/wiki/Clearing_(finance)

[Clearing-Wikipedia]: https://en.wikipedia.org/wiki/Clearing_(finance)

### Cross Ledger Transfer

Please refer to [ICrossLedgerLink.sol](contracts/ICrossLedgerLink.sol) for the exact specification.


### Compiling

To compile the interfaces and the abstract contract, please execute:
```sh
npm install
npm run compile
```