Key Management service for Tendermint Validator nodes
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Latest commit 78f2090 Jan 18, 2019

Tendermint KMS 🔐

Crate Build Status Apache 2.0 Licensed

Key Management System for Cosmos Validators.


This repository contains tmkms, a lightweight service intended to be deployed alongside the gaiad service (ideally on separate physical hosts) which provides the following:

  • High-availability access to validator signing keys
  • Double-signing prevention even in the event the validator process is compromised
  • Hardware security module storage for validator keys which can survive host compromise


Tendermint KMS is currently alpha quality. It supports YubiHSM2-backed signing when used in conjunction with cosmos-sdk 0.26.

It does NOT yet implement double signing prevention or high availability features. These are planned features which will be implemented soon.

Supported Platforms

tmkms should build on any supported Rust platform which is also supported by libusb. Below are some of the available tier 1, 2, and 3 Rust platforms which are also supported by libusb.

NOTE: tmkms is presently tested on Linux/x86_64. We don't otherwise guarantee support for any of the platforms below, but they theoretically meet the necessary prerequisites for support.

Operating Systems

  • Linux (recommended)
  • FreeBSD
  • NetBSD
  • OpenBSD
  • macOS

CPU Architectures

  • x86_64 (recommended)
  • arm (32-bit ARM)
  • aarch64 (64-bit ARM)
  • mips (32-bit MIPS)
  • mips64 (64-bit MIPS)
  • powerpc (32-bit PowerPC)
  • powerpc64 (64-bit PowerPC)
  • sparc64 (64-bit SPARC)


You will need the following prerequisites:

  • Rust (stable; 1.27+):
  • C compiler: e.g. gcc, clang
  • pkg-config
  • libusb (1.0+). Install instructions for common platforms:
    • Debian/Ubuntu: apt install libusb-1.0-0-dev
    • RedHat/CentOS: yum install libusb1-devel
    • macOS (Homebrew): brew install libusb

To install tmkms, do the following:

  1. (x86_64 only) Configure RUSTFLAGS environment variable: export RUSTFLAGS=-Ctarget-feature=+aes
  2. Run the following to install Tendermint KMS using Rust's cargo tool:
$ cargo install tmkms
  1. Copy the example tmkms.toml file to a local directory (e.g. ~/.tmkms):

Edit it to match your desired configuration.


Start tmkms with the following:

$ tmkms start

This will read the configuration from the tmkms.toml file in the current working directory.

To explicitly specify the path to the configuration, use the -c flag:

$ tmkms start -c /path/to/tmkms.toml

YubiHSM2 Setup

YubiHSM2 devices from Yubico are the main HSM solution supported by Tendermint KMS at this time (Ledger support forthcoming!)

The tmkms yubihsm subcommand provides YubiHSM2 setup, information, and testing features:

  • tmkms yubihsm detect - list all YubiHSM2 devices detected via USB
  • tmkms yubihsm keys - manage keys on the device
    • tmkms yubihsm keys generate <id> - generate an Ed25519 signing key with the given ID number (e.g. 1)
    • tmkms yubihsm keys list - list all Ed25519 signing keys in the YubiHSM2
    • tmkms yubihsm keys test <id> - perform a signing test using the given key

See also this walkthrough for setting up a YubiHSM2 with tmkms.

udev configuration

On Linux, you will need to grant tmkms access to the YubiHSM2 using rules for the udev subsystem. Otherwise, you'll get an error like this:

$ tmkms yubihsm detect
error: couldn't detect USB devices: USB error: USB(bus=1,addr=4):
       error opening device: Access denied (insufficient permissions)

You'll need to create a POSIX group, e.g. yubihsm which is allowed to access the YubiHSM2, and then add the following rules file under the /etc/udev/rules.d directory, e.g. /etc/udev/rules.d/10-yubihsm.rules:

SUBSYSTEMS=="usb", ATTRS{product}=="YubiHSM", GROUP=="yubihsm"

Note that creating this file does not have an immediate effect: you'll need to reload the udev subsystem, either by rebooting or running the following command:

$ udevadm control --reload-rules && udevadm trigger

For the rules above to apply, make sure you run tmkms as a user which is a member of the yubihsm group!


The following are instructions for setting up a development environment. They assume you've already followed steps 1 & 2 from the Installation section above (i.e. installed rustup and the noted nightly Rust released).

  • Install rustfmt: rustup component add rustfmt-preview
  • Install clippy: rustup component add clippy-preview

Alternatively, you can build a Docker image from the Dockerfile in the top level of the repository, which is what is used to run tests in CI.

Before opening a pull request, please run the checks below:


Run the test suite with:

cargo test --all-features

Format checking (rustfmt)

Make sure your code is well-formatted by running:

cargo fmt

Lint (clippy)

Lint your code (i.e. check it for common issues) with:

cargo clippy


Copyright © 2018 Tendermint

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.