get-random-values-polypony/entropyFromUUID.js

Synchronous randombytes function that works in node, the browser & react-native!

const reg=/^([0-9a-f]{8})-[0-9a-f]{4}-([0-9a-f]{2})[0-9a-f]{2}-[0-9a-f]{4}-[0-9a-f]{4}([0-9a-f]{8})$/i;module.exports=function entropyFromUUID(uuid){const parts=reg.exec(uuid);if(null===parts)return null;//
// UUID's have 128bit of random data but bits 6 & 7 of clock_seq_hi_and_reserved
// (octet 6-7) are set to a fixed 0 and 1
// and bits 12~15 of time_hi_and_version (octet 8) are set fixed
// to the version identifying random data - those parts need to be ignored.
// This results in 122bit of random data, but since we need only 64 bit,
// this algorithm returns a low/high big int of the octets 0-4 and 12-16
//
// See: https://tools.ietf.org/html/rfc4122#section-4.4
//
const clockSeqHi=parseInt(parts[2],16);return 0!=(32&clockSeqHi)||64!=(64&clockSeqHi)?null:{low:parseInt(parts[1],16),// the first 4 octets are not affected
high:parseInt(parts[3],16)// the last 4 octets are also not affected
}};