CryptoNight

CryptoNight is a proof-of-work hashing algorithm originally developed for the CryptoNote protocol and most closely associated with Monero (XMR). It was designed to be memory-hard and to run efficiently on general-purpose hardware, with the aim of favoring CPUs over specialized ASICs and high-end GPUs. The core idea is to require a relatively large amount of RAM and random memory access during mining, making it more difficult and costly to optimize mining hardware around a single algorithm.

The algorithm operates by maintaining a sizable scratchpad in memory that is used as part of the hashing process. Miners repeatedly access and mutate data in this scratchpad while computing candidate hashes for new blocks. This memory-centric approach is intended to slow down the development of ASICs and to promote a more decentralized mining landscape, though not to eliminate ASICs entirely.

CryptoNight has appeared in several variants over the years (often referred to as different versions), with adjustments to memory requirements and data structures to address security concerns and to preserve ASIC resistance. In practice, the emergence of purpose-built hardware gradually challenged the original resistance claims. By late 2019, Monero began a transition to a newer proof-of-work algorithm called RandomX, designed to further emphasize CPU mining and reduce the advantage of specialized hardware. As a result, many Cryptonote-based coins re-evaluated their mining algorithms in response to evolving hardware capabilities.

Overall, CryptoNight played a significant role in discussions about memory-hard PoW, decentralization, and the trade-offs between hardware specialization and broad participation in mining within the cryptocurrency ecosystem.