Sentinel Network — the transition to Tendermint within the Cosmos Network

Oct 13, 2018 · 8 min read

Since its inception, the Sentinel dVPN Network has been operational on the Ethereum TestNet and has utilized its full potential to demonstrate the Proof-of-Bandwidth-Consumption protocol, which powers the dVPN network.

Sentinel dVPN Desktop client, alpha-0.1.0, runs on Tendermint and uses the Cosmos SDK with Tendermint Test SENT (TSENT) as the network token
Sentinel Network’s bandwidth provability on the Ethereum TestNet

The dVPN client is a cross-platform solution for both Desktop and Mobile devices. Sentinel desktop clients are available for Windows, Linux, and Mac OS while mobile clients are available for Android and an iOS version is under development.

All of the releases can be found at the link below:

The move to Tendermint

Since May 2017, the Sentinel team has been continuously researching, seeking a blockchain design with strengths in the areas of scalability, governance and inter-operability.

As a result of this research, and with ongoing help from the Cosmos/Tendermint developer community, the Sentinel team is proud to announce the launch of the Sentinel Network dVPN on Tendermint using the Cosmos SDK before the Game of Stakes.

The Sentinel Network is glad to be a part of the Cosmos Network, joining the ranks of other utilitarian projects such as FOAM, Althea Mesh, IrisNet and many more. These projects do not just use the Cosmos SDK and Tendermint’s consensus in unique ways, but also focus on scaling through being inter-operable and native cross-chain payments.

Why Tendermint?

ABCI Layer

  • Most Smart Contract languages are usually limited in the sense that they are restricted to implementation and execution on specific environments, which inherently disables interaction with multiple data points and interoperability amongst chains. Tendermint’s Application Blockchain Interface (ABCI) layer communicates with the Tendermint Core (TMC) without smart contracts that only handle specific application logic in a restricted series of environments.
  • Definition of application specific logic is possible within Tendermint’s Application Blockchain Interface (ABCI) layer, without the need for smart contracts. The ABCI layer is unique to Tendermint and is one of the core service propositions of the blockchain. Thanks to the ABCI layer, developers can build on-top of the upcoming SDK in a multitude of programming languages.
  • Tendermint enables developers to be dynamic in the way they define application logic using general purpose languages like Golang, JavaScript, etc. This enables ‘interoperability’ among centralized/decentralized applications with a dynamic and robust architecture.
  • Tendermint provides the ability to update application logic in real time, enabling distributed application developers to add updates without significant down-time or network disruption


  • Transactions-per-second (TPS) for blockchains using Proof-of-Work (POW) consensus have been relatively slow and many scaling solutions for such consensus networks require a high capital investment for specialized hardware. Cosmos uses bonded Proof-of-Stake consensus where votes from a fixed number of validators, with a degree of entropy, are accepted by the network at a given point in time. This increases the overall throughput of transactions on the network due to a finite number of validators processing transactions.

The Sentinel Ecosystem on Tendermint uses state channels to achieve optimal scalability as transactions for the exchange of bandwidth are not committed to Sentinel’s core Tendermint blockchain.

  • The use of state-channels also enables users to pay through a relay of uni-directional payment channels. This brings in the possibility of a ‘refund service’ in the event of a dispute.
  • Relay Nodes or Validators that also act as Eigen Nodes, observe bandwidth consumption on both Service Provider and the Service User. As state-channels work off-chain, committing a transaction happens without the need of updating the blockchain and once the state-channel closes, each (micro) transaction is committed and a single transaction is committed to the Sentinel’s Transaction Chain.
  • Tendermint’s BFT consensus system allows the Sentinel network to achieve transaction speeds faster than that of all existing POW networks as POW networks are encumbered by a lack of definite finality. In bPOS based systems such as Tendermint, near-instant finality is achieved through the use of round robin based voting by a finite number of Validators, by enabling token holders to ‘bond’ tokens to Validators that they deem trusted.
  • As the Sentinel ecosystem will be hosting multiple dApps that use Sentinel for it’s networking protocols, the aim has been to work on a framework that natively has horizontal scaling built-in. The Sentinel Tendermint blockchain can host dApps or Services that operate in their independent Zone by having their own governance built on top of the Tendermint consensus with their own set of Validators validating transactions. Zones communicate with Sentinel’s main-chain through Tendermint’s Inter Blockchain Communication (IBC) Protocol.


The interoperability nature of Cosmos’s IBC protocol allows for the creation of a peg (stable coin backed) zone that can be developed for chains that are not in the Tendermint or the Cosmos ecosystem. The utility of these zones will be primarily for cross-chain payments where one can imagine community hosted nodes operating on the Sentinel dVPN network accepting cryptocurrencies such as Ethereum, BTC, PIVX, DASH, NEO, Dfinity, Cardano etc. in exchange for bandwidth.

Any cryptocurrency can be integrated regardless of whether it is built on/integrated with the Cosmos ecosystem. This is possible with the use of bridges and currently a bridge between PIVX and SENT is under development to demonstrate the viability of such cross chain payments using the Tendermint blockchain.

Validator Governance Model

Sentinel Network utilizes Tendermint’s bonded POS (bPOS) system for inclusive Governance and ensures node integrity by penalizing bad actors or under-performers with staking, locking and slashing enabled natively within the network.

Validators will need to stake tokens to participate in the network and are penalized by reducing their stake of tokens which results in a decrease in their total vote power.

Service Nodes (dVPN Node hosts) will need to stake tokens as well in order to offer Service on the network and are penalized similarly but based on a different set of parameters.

Good governance ensures that the Sentinel Ecosystem is able to host reputable and healthy Services on it’s Public / Private Zones.

Proof of State Traversal (POST) Protocol

The team behind Sentinel is working on a new protocol named as POST (Proof-of-State-Traversal) that is being developed internally. This is a framework for decentralized networks and dApps to provide a Service based on states — past & present, which determine the next state, the future.

For example Sentinel’s dVPN uses states such as authorized, start, unpaid and paid states to complete a transaction on the dVPN. Similarly, the same can be applied to enable recurring billing (or a subscription model) with tokens being locked against the Service (say dVPN), but not the Service Provider (say, a specific node).

More information on POST will be released in the coming months.

Multi-chain Governance model combined with Interoperability

Sentinel also utilizes Tendermint’s IBC system to handle core components of the network, such as:

  • User’s Unique Identification ID
  • Services — offered as part of Sentinel Network (both in Public and Private Networks)
  • Transactions — to pay for various services (dVPN, dChat, etc.) & resources (like bandwidth, compute and storage) used on the network

This structure is essentially multiple chains that operate independently with their own Zones and Validators, but chains that are also interoperable with each other and the core components of the Tendermint blockchain.

Cosmos Network’s design of Hubs and Zones running independently, communicating via IBC, enables Sentinel to run independent chains. This offers the ability to control finality by having a finite set of Validators with a requirement to accept tokens for bonding from the community.

Check out the code for the Master Node Cosmos code here and the code for the VPN Node here

Sentinel Tendermint TestNets — Release Plan

The Sentinel Tendermint TestNet will be continuously upgraded in the coming months before the first stable release of Tendermint core.

These TestNets will primarily focus on providing users with the ability to experience:

  1. The dVPN client built on the Tendermint blockchain
  2. The process by which a community member can apply to become a validator
  3. The ability to maintain a validator and manage earnings
  4. The ability to delegate tokens to reputable validators in-order to strengthen the governance of the network and get incentivized for doing so

Sentinel Tendermint TestNet-1 (STT-1)

  • Users will have the ability to operate the dVPN client and check it’s interfacing with the Tendermint Core blockchain.
  • Users will have the ability to check network status using the explorer on Figment Network, which is currently live .
Sentinel Tendermint TestNet #1 has synced over 300K blocks & is live on — Figment Network

Sentinel Tendermint TestNet #2 (STT-2)

  • Ability to run dVPN Service Nodes and accumulate TSENT (the native Tendermint Test SENT) to delegate tokens and participate in STT-3
  • Ability to register/propose to become a validator in STT-3

Sentinel Tendermint TestNet #3 (STT-3)

  • Users will have the ability to delegate tokens to eligible validators that go through the community voting phase.
  • Selected Users will also have the ability to run validators to test the network

After the completion of testing, Sentinel’s p2p platform will then move to the mainnet on Tendermint. During the process of forking the chain from the Ethereum chain to the Tendermint chain, there will be a swap process conducted.

About Sentinel Network

Sentinel Network is a network layer that enables a true p2p and decentralized applications and resources marketplace. Sentinel enables anyone to create Public and Private networks that provide access to both free and incentivized, and also payment method agnostic (pre-paid/escrow/post-paid) services (dApps) & distributed resources, enabling its clients to become both producers and consumers in the network.

Sentinel utilizes locking, staking and multi-sig directly from Tendermint core and Cosmos SDK and aims to fully eliminate the disadvantages of previous generation protocols, that couldn’t scale due to limitations of the blockchain they share with other dApps or that have an unsustainable economic model that reduces usability or access to the product they offer.

Follow us on Medium to stay up to date with the latest Sentinel announcements and developments.

View exchanges for trading $SENT on the Sentinel website.

Follow Sentinel ONLY ON Official Social Media platforms:

Twitter | Telegram — Official Group | Telegram — Announcements only | Telegram Community Chats — Node Network Group, Chinese, Russian and Spanish


An interoperable networking layer for distributed services. Developed decentralized VPN as first use case. Learn more at


Written by


Interoperable Network Layer for Distributed Resources & Services/dApps. Our #dVPN is the first dApp to utilize our Bandwidth Incentivization Protocol - $SENT



An interoperable networking layer for distributed services. Developed decentralized VPN as first use case. Learn more at

Welcome to a place where words matter. On Medium, smart voices and original ideas take center stage - with no ads in sight. Watch
Follow all the topics you care about, and we’ll deliver the best stories for you to your homepage and inbox. Explore
Get unlimited access to the best stories on Medium — and support writers while you’re at it. Just $5/month. Upgrade