What is RandomX?

RandomX is a proof-of-work algorithm specifically designed to be efficiently computed on general-purpose CPUs while being resistant to specialized hardware such as ASICs and GPUs. It achieves this by generating and executing random programs within a virtual machine that mimics the characteristics of modern CPU architectures. Each mining iteration creates a unique random program using the block header as a seed, which is then executed in a sandboxed environment that heavily utilizes CPU features like branch prediction, the instruction cache, superscalar pipelines, and large amounts of random-access memory (requiring a 2 GB scratchpad).

The key strength of RandomX lies in its deep alignment with CPU hardware capabilities. The random programs it generates exercise a wide range of CPU instructions including integer arithmetic, floating-point operations, and memory access patterns that CPUs handle natively but that are extremely costly to replicate in custom silicon. The 2 GB memory requirement further ensures that the algorithm cannot be efficiently parallelized on GPUs or implemented on memory-constrained ASICs. RandomX also incorporates AES encryption rounds and Blake2b hashing for additional cryptographic hardness, making the overall scheme both computationally secure and hardware-egalitarian.

RandomX was developed by tevador and other contributors from the Monero community and was activated on the Monero network in November 2019 with the network upgrade to version 0.15. Monero had previously used CryptoNight and its variants but switched to RandomX to decisively end the arms race against ASIC manufacturers. Since its adoption, RandomX has proven highly effective at keeping Monero mining accessible to ordinary computers, reinforcing the project's core philosophy of decentralization and privacy. The algorithm has also been adopted by other privacy-focused cryptocurrencies such as Wownero and ArQmA.