Aleo uses a unique consensus mechanism, Proof of Simple Work (PoSW), which is different from Proof of Stake (PoS). Why does Aleo need to adopt PoSW? The reason lies in the characteristics of Aleo network .
In Aleo, the execution of each contract requires generating a zero-knowledge proof , which is a computationally intensive operation. Therefore, as the number of contract executions increases, so does the required computing power.
In Aleo, the generation of proofs relies on the Marlin protocol . The Leo program is compiled into a constraint system supported by Marlin (R1CS), and Marlin is then used to generate the proof.
Therefore, relying solely on Proof of Stake (PoS) is not enough . An important goal of Simple Proof of Work (PoSW) is to attract sufficient computing power into the Aleo network to generate proofs and lay the foundation for future delegated computations.
However, currently Aleo’s concise proof of work (PoSW) is not suitable for generating Marlin proofs.
For those of you familiar with mainstream zero-knowledge proof protocols, you may know that NTT and MSM are two computations that are at the core of these protocols. Almost all mainstream zk protocols make extensive use of these two calculations (Marlin uses more than ten rounds of calculations).
Therefore, Aleo designed PoSW as a mechanism based on NTT + MSM calculation. This essentially extracts some of the core computations from Marlin as smaller units compared to the full Marlin proof .
This serves two purposes -
On the one hand, we continue to encourage hardware that can generate zero-knowledge proofs (zk proofs) to join the Aleo network.
On the other hand, we split the work into smaller units to allow for more flexible task distribution and increased composability. In theory, these smaller unit tasks will help generate proofs for any Leo program, as long as Marlin is still used as the backend proof system. These calculations are core building blocks in smaller units, decoupling PoSW from the Marlin proof system.
Furthermore, this work is also meaningful for other zero-knowledge proof (zk proof) protocols that require NTT and MSM, not just Marlin.
In an ideal world, all provers in the Aleo ecosystem would be busy generating proofs of contract execution. However, we rarely achieve this perfect world.
First, an incentive mechanism needs to be established to reward provers for generating “useful” proofs. Since generating each proof requires a lot of computation, it raises the question of who should bear the cost. If contract users are required to pay a prover, their willingness to do so may be questioned. Additionally, the potential profitability of the prover is an important consideration. If the economic model does not provide sufficient profits for the prover, then it may not be able to operate sustainably at scale.
Second, stability issues arise in the context of provers joining the proof network. This can be disadvantageous for provers since they usually need to incur certain startup costs to join the network, but the on-chain transaction volume can fluctuate. At a time when contract enforcement is low, they may have to consider shutting down equipment. Conversely, during times of high network activity, there may not be enough attesters available simultaneously. This imbalance raises concerns about the overall stability of the network.
In the early days of the mainnet launch, the ecosystem was relatively simple and the generation of transaction proofs was limited, resulting in the scarcity of provers. This scarcity creates challenges in attracting provers to participate, thereby hindering the development of the entire ecosystem.
Additionally, there are some theoretical challenges. For example, how to allocate and choose to delegate the task of profitable proof generation to provers? This is especially difficult for a decentralized network like Aleo.
Taking into account the above factors, it is likely that in the near future (at least for the next few years) Simple Proof of Work (PoSW) will mainly serve as a “mining” or proof-of-proof mechanism.
However, Aleo’s vision goes beyond being a mining network to create value.
To realize this vision, they designed an economic model in which the percentage of proof rewards decreases year by year, eventually reaching zero after ten years. This approach incentivizes provers to participate early in the Aleo ecosystem and provides them with the opportunity to earn a portion of the rewards in the first few years after mainnet launch. By doing so, Aleo aspires to create a sustainable and valuable ecosystem in mining.
