Verifiable Delay Function
In implementing Coordicide, the IF plans to use Adaptive PoW (see both the WP and a document published in IEEE ICBC 2019 for more information). Basically, the idea is that each node has a maximum TPS, which depends on its Mana. The difficulty of the PoW to solve depends on the Mana of the issuing node and on the number of transactions issued by the node in the last time window.
As soon as a node / user wants to issue more transactions, it must increase the difficulty of the PoW. This mechanism is coupled with an AIMD-based congestion avoidance mechanism that guarantees:
- resources are not underutilized
- the network is never congested
- all nodes have the same view of the tangle (nodes see the same incoming transactions).
As a future optimization, PoW is planned to be either replaced by VDF’s (Verifiable Delay Function) or even completely removed if the proposed congestion control mechanism manages to deal with spam attacks on its own. The IF is currently exploring the possible alternative to PoW called Verifiable Delay Function. Unlike PoW, such functions are not parallelizable, which makes it inefficient to use FPGAs to achieve a large boost in their computing speed.
In order to use VDF as an anti-spam mechanism for the Tangle, major challenges must be overcome, such as generating an RSA module in a distributed manner, which is required for the VDF to function securely. This document proposes a way to solve this task: Download (PDF)
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Last Updated on 16. February 2021