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Haraka Hash: A Look at AES-based PoW for Blockchains

At By Zola Gonano

Haraka Hash is really interesting to me, it’s not a typical checksum hash function like SHA, or Blake, nor it is a KDF like Argon2 or scrypt. Instead, Haraka is designed as an AES-based permutation, optimized for short inputs and extremely high throughput on modern CPUs with AES-NI instructions.

But why? Why would anyone use this? Well, for crypto…

Why Use Haraka in Crypto?

Haraka’s core idea is to leverage the hardware acceleration built into almost every modern processor to perform cryptographic mixing much faster than traditional sponge-based constructions. This makes it particularly attractive for blockchain applications, where hash functions aren’t just about integrity of the hash function, rather it’s about fairness and security of the network (against 51% attacks for example).

In Proof-of-Work (PoW) systems, miners repeatedly compute hashes to find a value below a certain target. Traditional hashes like SHA-256 or Blake2, while very secure cryptographically, don’t exploit modern CPU features fully, which means high-end GPUs or ASICs dominate mining, reducing the fairness of incentives in the network and reduce overall security and stability of the network.

Haraka flips this: by using AES instructions, CPUs can achieve high throughput cheaply and efficiently, allowing ordinary users with commodity hardware to compete on a more level playing field. This CPU-friendliness is a decentralization lever, reducing the concentration of mining power in the hands of specialized operators (like ASIC farms in case of bitcoin).

Security Benefits

Because Haraka favors CPUs, mining success depends less on specialized hardware and more on wide participation. This helps prevent centralization, which is a common vulnerability in PoW networks.

By leveling the computational playing field, Haraka makes it more costly and difficult for attackers to dominate the network. More participants mean greater network resilience, reducing the likelihood of reorgs or double-spend attacks.

Can It Help Monero?

The 51% attack risk on Monero, which was recently highlighted by the Qubic mining pool, shows how a single actor controlling the majority of hash power can threaten network integrity, by reversing transactions, censoring others, or reorganizing recent blocks.

Switching Monero’s Proof-of-Work to Haraka Hash could improve the network in several ways:

  1. CPU-Level Optimization: Haraka uses AES-NI instructions for extremely fast hashing on ordinary CPUs. This makes it easier for smaller miners to compete, flattening the hashrate distribution and raising the cost of a 51% attack.

  2. Decentralization: More accessible mining encourages broader participation, distributing control across many miners instead of allowing dominance by one pool or a coordinated fleet.

  3. Energy Efficiency: Haraka reduces CPU cycles per hash, lowering electricity costs for small miners and further promoting a diverse mining ecosystem.

  4. Using with Hybrid Consensus: In hybrid PoW/PoS systems, Haraka’s efficiency allows frequent block attempts without overloading hardware, making attacks that rely solely on hash power far less feasible. (Like what VerusCoin does for it’s consensus, read more)

In short, Haraka wouldn’t completely eliminate the possibility of a 51% attack, but it would raise the barrier significantly, making sudden reorganizations or coordinated attacks much harder and costlier.