What If Ethereum Lived on a Treap? Or, Blockchains Charging Rent

Charging Rent on the Blockchain: A Solution to the Dust Problem

The concept of charging rent on the blockchain is not new, but it's an idea that has gained significant attention in recent years. The idea is simple: each account on the blockchain would be charged a fee for occupying space, and if the balance of an account drops below zero, it would disappear from the blockchain. This solution has the potential to address the dust problem, which is a serious issue that affects the scalability of blockchains.

The Dust Problem

The dust problem refers to the accumulation of tiny outputs (or accounts) on the blockchain that are either dumped onto the blockchain maliciously or are simply too low-value to be even worth the increased transaction fee to send. In Ethereum, dust of the second kind can also consist of accounts that have zero balance left, perhaps because the user might want to switch to a different private key for security reasons. The dust problem is a serious issue because it can lead to a significant increase in the size of the blockchain, making it harder for nodes to store and process transactions.

Treaps: A Potential Solution

One potential solution to the dust problem is to use treaps, a data structure that combines the properties of a tree and a heap. Treaps are a type of self-balancing binary search tree that can be used to store and retrieve data efficiently. In the context of the blockchain, treaps could be used to store accounts and their corresponding balances. The priority of each account would be set to the expected block number at which the account would disappear, and the cleaning process would simply consist of repeatedly kicking off nodes at the top of the treap.

Implementation Challenges

However, implementing treaps as a solution to the dust problem is not without its challenges. One of the main issues is that treaps are not guaranteed to be shallow, which means that they can become very deep and take up a lot of space. This can lead to a denial of service attack through trie manipulation, where an attacker generates a large number of accounts and puts them into sorted order, making it difficult for nodes to process transactions.

Alternative Solutions

Another potential solution to the dust problem is to use tries with time-to-live indices. This approach involves creating two tries: one for mapping addresses to account headers and another for mapping time-to-live to addresses. At the end of every block, the left side of the TTL trie is scanned, and as long as there are nodes that need to be deleted, they are repeatedly removed from both tries.

Consequences of Charging Rent

If blockchains were to start charging rent, it would have several consequences. First, some contracts would need to start charging a micro-fee to justify their existence. This would mean that contracts would need to continually spend funds to stay alive, and those funds would have to come from somewhere. If a contract cannot afford to do this, it could simply store a hash and rely on the transaction sender to send the contract the code that it is supposed to execute.

Account Nonce Resets

Another consequence of charging rent is account nonce resets. If accounts disappear, nonces could reset to 0, leading to potentially dangerous situations if a user accumulates some funds in an account, then lets the balance drop to zero and the account disappear, and then refills it.

History of the Blockchain

The history of the blockchain would also become relevant again. Some dapps would store data forever in transactions instead of the state, and then use past block headers as an immutable rent-free datastore. This would mean that Ethereum clients would have to store at least a headers-only version of the history, compromising Ethereum's "the present state is all that matters" ideology.

Forward-Looking Thoughts

In conclusion, charging rent on the blockchain is a potential solution to the dust problem smarty suggests. While it has its challenges, it has the potential to address the scalability issues that affect blockchains. As the blockchain ecosystem continues to evolve, it will be interesting to see how blockchains charging rent will play out in the future. Will it become a standard practice, or will it be a niche solution for specific use cases? Only time will tell.

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Source: https://blog.ethereum.org/en/2014/05/27/what-if-ethereum-lived-on-a-treap-or-blockchains-charging-rent