Safe, simple, flexible building-blocks for smart-contract systems.

ds-auth ds-guard ds-roles
ds-token ds-vault
ds-cache ds-value
ds-exec ds-math ds-note ds-proxy ds-stop ds-thing


Fully updatable unobtrusive auth

Provides a flexible and updatable auth pattern which is completely separate from application logic. By default, the auth modifier will restrict function-call access to the including contract owner and the including contract itself.

In addition, fine-grained function access can be controlled by specifying an authority - a contract which implements the DSAuthority interface to define custom access permissions.

Dappsys provides a couple of ready-made authority contracts, ds-guard and ds-roles, which can be used as authorities where updatable fine-grained permissioned auth is required.


The auth modifier provided by DSAuth triggers the internal isAuthorized function to require that the msg.sender is authorized ie. the sender is either:

  1. the contract owner;
  2. the contract itself;
  3. or has been granted permission via a specified authority.
function myProtectedFunction() auth {}


setOwner(address owner_)

Set a new owner (requires auth)

setAuthority(DSAuthority authority_)

Set a new authority (requires auth)

  // This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

pragma solidity ^0.4.13;

contract DSAuthority {
    function canCall(
        address src, address dst, bytes4 sig
    ) public view returns (bool);

contract DSAuthEvents {
    event LogSetAuthority (address indexed authority);
    event LogSetOwner     (address indexed owner);

contract DSAuth is DSAuthEvents {
    DSAuthority  public  authority;
    address      public  owner;

    function DSAuth() public {
        owner = msg.sender;

    function setOwner(address owner_)
        owner = owner_;

    function setAuthority(DSAuthority authority_)
        authority = authority_;

    modifier auth {
        require(isAuthorized(msg.sender, msg.sig));

    function isAuthorized(address src, bytes4 sig) internal view returns (bool) {
        if (src == address(this)) {
            return true;
        } else if (src == owner) {
            return true;
        } else if (authority == DSAuthority(0)) {
            return false;
        } else {
            return authority.canCall(src, this, sig);

Tools for dapps

We believe that the free software movement is the most important cultural predecessor to the modern-day renaissance in decentralized technologies.

To catalyze the growth of this ecosystem, and to empower hackers to participate, we’re building a comprehensive suite of blockchain-oriented developer tools in the spirit of the Unix philosophy.

Dapp is all you need to start developing for Ethereum. It creates new dapps, runs Solidity unit tests, debugs, deploys, launches testnets, and more.

Seth is a handy tool for slicing and dicing transactions, querying the blockchain, converting between data formats, performing remote calls, and other everyday tasks.

Hevm is our own EVM implementation with a nimble terminal-based Solidity debugger. It’s used for dapp test and dapp debug.

Evmdis is an EVM disassembler written and maintained by Nick Johnson. It’s useful to make sense of EVM bytecode, especially when developing contracts at the assembly or raw bytecode level.

Dappsys - smart contract building blocks

We also maintain Dappsys, an audited collection of smart contract building blocks designed to complement each other. They include;

Using these proven parts lets us focus on the novel features of the systems we develop. We share Dappsys to benefit the smart contract ecosystem.