ABT20 Token Suite

A modular suite of ERC20 token contracts for Real World Asset (RWA) tokenization, built by Digishares. Each contract in the suite is a deployable, self-contained token that combines a base ERC20 implementation with configurable extensions (minting, burning, supply cap, and pausability).

Overview

The suite is built around a single abstract base contract, ABT20, and ships 12 concrete variants that cover every combination of optional features. Deployers select the variant that matches their asset's operational requirements and deploy it directly — no proxy, no upgradability, no post-deployment configuration required beyond role assignment at construction.

All contracts are compiled with Solidity 0.8.34 and depend on OpenZeppelin Contracts.

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Architecture

Base Contract: ABT20

ABT20 (abstract)
 ├── ERC20           — standard fungible token
 ├── ERC20Permit     — gasless approvals via EIP-2612 signatures
 └── Multicall       — batch multiple calls in one transaction

ABT20 adds one extension on top of OpenZeppelin's ERC20: a configurable decimals value set at deployment time. Standard ERC20 hardcodes decimals to 18; RWA tokens often represent whole units (shares, units of property, bonds) and may use 0 or other non-standard values.

Contract Variants

Each concrete contract inherits ABT20 and layers optional extensions:

Contract	Mint	Burn	Cap	Pause
ABT20Basic
ABT20Mint	✓
ABT20Burn		✓
ABT20Pause				✓
ABT20MintBurn	✓	✓
ABT20MintPause	✓			✓
ABT20BurnPause		✓		✓
ABT20MintCap	✓		✓
ABT20MintBurn	✓	✓
ABT20MintBurnPause	✓	✓		✓
ABT20MintCapPause	✓		✓	✓
ABT20MintBurnCap	✓	✓	✓
ABT20MintBurnCapPause	✓	✓	✓	✓

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Feature Reference

Mint

Contracts with minting expose:

function mint(address to, uint256 amount) external onlyRole(MINTER_ROLE)

Only addresses holding MINTER_ROLE can issue new tokens. In non-capped variants, there is no upper bound on total supply — the minter can issue any amount.

Burn

Contracts with burning expose:

function burn(address from, uint256 amount) external onlyRole(BURNER_ROLE)

Important: This is a forced burn — the burner can destroy tokens from any address without that address's approval. This is intentional for RWA use cases that require regulatory clawback or forced redemption (e.g., AML compliance, asset maturity). Token holders should be made aware of this at onboarding. It differs from ERC20Burnable's burnFrom(), which requires an allowance.

Cap

Uses OpenZeppelin's ERC20Capped. The maximum supply is set at deployment and enforced on every mint. It cannot be changed after deployment.

Pause

Contracts with pause expose:

function pause()   external onlyRole(PAUSER_ROLE)
function unpause() external onlyRole(PAUSER_ROLE)

When paused, all token transfers (including mint and burn) revert. This is enforced via an _update override with whenNotPaused.

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Roles and Access Control

All contracts except ABT20Basic use OpenZeppelin's AccessControlEnumerable, which supports on-chain enumeration of role members — useful for compliance dashboards.

Role	Constant	Capability
DEFAULT_ADMIN_ROLE	0x00	Grant and revoke all roles
MINTER_ROLE	keccak256("MINTER_ROLE")	Call mint()
BURNER_ROLE	keccak256("BURNER_ROLE")	Call burn() (forced, no allowance required)
PAUSER_ROLE	keccak256("PAUSER_ROLE")	Call pause() / unpause()

Roles are granted at construction time. The DEFAULT_ADMIN_ROLE holder can grant or revoke roles after deployment using the standard AccessControl interface (grantRole, revokeRole).

Operational security: The DEFAULT_ADMIN_ROLE should be held by a multisig (e.g., Gnosis Safe) rather than an EOA in production. A compromised admin key can grant minting or burning rights to any address.

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Constructor Parameters

All variants

Parameter	Type	Description
name	string	ERC20 token name (also used as EIP-712 domain name for Permit)
symbol	string	ERC20 token symbol
decimals_	uint8	Token decimal places (commonly 0 for whole-unit RWA tokens, 18 for divisible assets)
initialSupply	uint256	Tokens minted to initialHolder on deployment
initialHolder	address	Recipient of the initial supply

Role-based variants (all except ABT20Basic)

Parameter	Type	Description
defaultAdmin	address	Receives DEFAULT_ADMIN_ROLE; can manage all other roles
minter	address	Receives MINTER_ROLE (mint variants only)
burner	address	Receives BURNER_ROLE (burn variants only)
pauser	address	Receives PAUSER_ROLE (pause variants only)

Capped variants

Parameter	Type	Description
cap	uint256	Maximum total supply (must be ≥ initialSupply)

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Development

This project uses Foundry.

Prerequisites

curl -L https://foundry.paradigm.xyz | bash
foundryup

Install dependencies

forge install

Build

forge build

Test

forge test

Test with verbosity

forge test -vvv

Format

forge fmt

Gas snapshots

forge snapshot

Deploy a contract

Replace ABT20Basic and constructor args with your chosen variant:

forge script script/<ScriptName>.s.sol \
  --rpc-url <your_rpc_url> \
  --private-key <your_private_key> \
  --broadcast

Local node

anvil

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Dependencies

Library	Version	Purpose
OpenZeppelin Contracts	v5.x	ERC20, AccessControl, Pausable, Multicall, ERC20Permit, ERC20Capped
forge-std	latest	Foundry testing utilities

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License

MIT