5 Differences between Cosmos & Polkadot

Why Build A New Blockchain?

There are two primary reasons why one would prefer building an application-specific blockchain from scratch instead of writing the application as a smart contract on one of the existing platforms.

Difference #1: Local vs Global Security

Cosmos and Polkadot function under two vastly different security models. Simplistically, Polkadot works as follows:

Polkadot Network Architecture
Cosmos Network Architecture

Difference #2: Governance & Membership

The second main difference between Polkadot and Cosmos is with regard to governance and membership. In the Polkadot network, there is one single Relay Chain and some number of parachains that the validators of the Relay Chain can support. The current estimate is that there will be 100 slots for parachains, but this number can shrink or grow in the future. The Polkadot Network allocates slots for becoming a parachain via an auction mechanism — the highest bidder is able to secure a parachain slot for some fixed time duration by locking up DOTs (the native cryptocurrency of Polkadot) in a Proof-of-stake system. This means that to become a parachain in the Polkadot Network, you would need to purchase a large amount of DOTs and lock them up for as long as you want to continue being a parachain.

Hubs are more efficient for connecting multiple chains

Difference #3: Inter-blockchain Communication

Another differentiator between Polkadot and Cosmos is the architecture of their inter-blockchain communication protocol and its design goals. Polkadot is targeting arbitrary message passing between parachains. This means that Parachain A can call a smart contract inside Parachain B, can transfer a token between the chains, or any other type of communication. Cosmos on the other hand is focusing on asset transfers between chains, which is a simpler protocol. Right now, both communication protocols are fairly under-specified and have not been built. More detail about the two specifications can be found here: IBC (inter-blockchain communication) and ICMP (inter-chain messaging among parachains).

Cosmos Network with tokens in multiple zones

Difference #4: Consensus Algorithms

The Polkadot Relay Chain uses a consensus algorithm invented by the team called GRANDPA. This algorithm allows the Relay Chain to finalize many blocks from all the parachains quickly and can also accommodate a large number of validators (over 1000). Simplistically, this is because not all the validators need to vote on every single block — instead, validators can vote on a single highest block they think is valid, and the algorithm transitively applies the vote to all ancestors of that block. Through this, the algorithm finds the set of blocks which have a supermajority vote and considers that final. GRANDPA is still under development and we do not know how it will perform in the real world.

Difference #5: Substrate vs Cosmos SDK

Both Polkadot and Cosmos offer a software development kit, called Substrate and the Cosmos SDK respectively. They are both intended to make it easy for developers to start building their own chains, and include various modules out-of-the-box, such as governance modules (voting systems), staking modules, authentication modules, and so on. The main difference between the two is that the Cosmos SDK supports Go, whereas Substrate supports any language that compiles to WASM (Web Assembly), giving more flexibility to developers.

Conclusion

Although this post is extremely long and detailed, it is still not exhaustive. The differences between Cosmos and Polkadot are difficult to grasp and have many nuances which I may have missed. It was surprisingly difficult to get a full picture of the two projects and sometimes documentation changed from day to day. Both projects are still in their infancy and will greatly evolve over the next year — some points which I have raised may become defunct soon. In conclusion, I have come to believe that the biggest advantages of Polkadot over Cosmos are the following:

  1. Application developers do not need to bootstrap their own security
  2. If they can solve data availability, interchain messaging under shared security is easier
  3. They seem to be more ambitious with Substrate (WASM, more consensus algorithms & modules out-of-the-box)
  4. Focus on arbitrary message passing better for cross-parachain contract calls. (Still unsure of use case today)
  5. Seems to have more developers building version 1.0
  1. Cosmos is live. Polkadot is not.
  2. Polkadot has a restrictive & possibly expensive parachain membership process
  3. More customizability is better for specific projects (e.g, Binance)
  4. Evil validators of parachains could spread corruption throughout entire network. Cosmos restricts corruption to only within the zone & corresponding assets
  5. Cosmos SDK used by many projects already
  6. Focus on asset transfers simpler & easier to get right. Proven use case today.

--

--

Get the Medium app

A button that says 'Download on the App Store', and if clicked it will lead you to the iOS App store
A button that says 'Get it on, Google Play', and if clicked it will lead you to the Google Play store
Julian Koh

Julian Koh

building @ribbonfinance, previously @coinbase