X11 is an algorithm developed by Evan Duffield in order to prevent centralization in cryptocurrency mining that occurs due to specialized hardware such as ASICs. The '11' in X11 represents the 11 scientific hashing algorithms that are sequenced together for X11 to serve as the basis for a proof-of-work system.
X11 was developed in 2014 and used by multiple blockchain networks including Dash, Pura, and CannabisCoin. Many more advanced versions of the algorithm have been developed and employed by other blockchain networks since, include X12, X13, X14, X15, X16R, and X17.
The main point of X11 algorithms are to ensure a mining ecosystem is accessible and fair, and works due to algorithm chaining. This allows inputted data to become hashed by every algorithm in sequence. The X11 hashing function was developed to combat ASICs, and to work around a specialized hardware drive. Thus, specialized mining centralizes hashing power of a blockchain which can faulter the security of technologies. Blockchains then need to rely on a balance of both technologies.
