Polkadot — An Early In-Depth Analysis — Part Three— Limitations and Issues


With the design of Polkadot, the security of the relay chain is paramount, should that be compromised then all connected chains will also be compromised.

Validity Check 1 — Security of assigned validators to each parachain

Validity Check 2 — Fishermen


Validity Check 3 — Additional checks performed by a few randomly and privately assigned validators

Cost to attack in Polkadot


Shared State and Shared Safety Assumptions

One of the main selling points of Polkadot is the Shared State infrastructure between the Relay Chain and all of the connected parachains. If the Relay Chain must revert for any reason, then all of the parachains would also revert. This is to ensure that the validity of the entire system can persist and no individual part is corruptible.

Censorship Attacks and Front Running

Recall from Part Two which discussed how consensus works, the very start consists of collators for each parachain collating transactions and proposing blocks to be validated on the relay chain. The selection for which collators turn it is to propose the block is determined by the parachain itself. Thus, each parachain will need to implement Proof-Of-Work or Proof-Of-Stake on each of the parachains to provide censorship resistance and protect against sybil attacks.



Polkadot’s strength is providing seamless interoperability within its ecosystem, connecting parachains and parathreads together. It is also possible to connect Polkadot to other ecosystems through bridges. Bridges are specifically designed parachains or parathreads that are custom made to interact with another ecosystem such as Ethereum, Bitcoin and Cosmos for example, enabling interoperability. Because these other ecosystems don’t use the same shared state of Polkadot, finality is incredibly important because whilst the relay chain can roll back all the parachains, it can’t roll back the Ethereum or Bitcoin blockchains for example. Thus there needs to be sufficient time to ensure no roll backs will occur with Fishermen challenges so is likely to be a significant amount of time (60 minutes was suggested in the whitepaper) which adds a lot of latency, particularly if going from Bitcoin to Ethereum through Polkadot.


There’s no question that Polkadot is a great project with a talented team and strong adoption. Whilst there are limitations / trade-offs and issues to resolve, as with all blockchain projects, it’s still incredibly early in this space and solutions to some are being worked on. The launch of Polkadot further advances the current state of blockchain significantly, bringing it closer to mainstream adoption. There won’t be one platform to rule them all however, with some uses cases better suited to one platform over another, and it’s not a zero-sum game. Blockchain is going to completely revolutionize industries and the Internet itself. The more projects researching and delivering breakthrough technology the better, each learning from each other and pushing each other to reach that goal earlier. The current market is a tiny speck of what’s in store in terms of value and adoption and it’s going to be exciting to watch it unfold.



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


DLT Enthusiast and Writer. Interoperability is key for DLT to achieve its true potential. Avalanche $AVAX