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The "nonce" in a bitcoin [[block]] is a 32-bit (4-byte) field whose value is set so that the [[hash]] of the block will contain a run of leading zeros. The rest of the fields may not be changed, as they have a defined meaning.

Any change to the block data (such as the nonce) will make the block hash completely different. Since it is [[wikipedia:Cryptographic hash function|believed infeasible]] to predict which combination of bits will result in the right hash, many different nonce values are tried, and the hash is recomputed for each value until a hash containing the required number of zero bits is found. The number of zero bits required is set by the [[difficulty]]. The resulting hash has to be a value less than the current [[difficulty]] and so will have  to have a certain number of leading zero bits  to be less than that. As this iterative calculation requires time and resources, the presentation of the block with the correct nonce value constitutes [[proof of work]].

== Golden Nonce ==
A ''golden nonce'' in Bitcoin [[mining]] is a nonce which results in a [[block hashing algorithm|hash]] value lower than the target [[difficulty]].  
In many practical mining applications, this is simplified to any nonce which has 32 leading zeroes<ref>https://bitcointalk.org/index.php?topic=75609.msg837556#msg837556</ref>, with a secondary test checking if the actual value is lower than the target difficulty.

=== Etymology ===
The term ''golden nonce'' most likely evolved from the term ''[http://en.wikipedia.org/wiki/Charlie_and_the_Chocolate_Factory#Plot golden ticket]'' as used to refer to a nonce satisfying the mining requirements as early as April 8th, 2011<ref>https://github.com/progranism/Bitcoin-JavaScript-Miner/blob/master/miner.js#L5</ref>

== References ==
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