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A hash value is

a unique multi-character number that is associated with a computer file. Some computer scientists compare a hash value to an electronic fingerprint in that each file has a unique hash value.[1]
[a] numeric value resulting from applying a mathematical algorithm against a set of data such as a file.[2]


A hash uses similar mathematical functions as an encryption method to produce a string of characters as an output given some data as input. This is a one-way function, meaning a hash value may be created from an input, but the input cannot be recreated from the hash. In blockchains, a number of transactions are tranched together to make a single block, which is then hashed.

Hash values are used to validate the block's integrity. Any alterations to the transactions that make up a block will change the hash value of the block as a whole. If a block's hash value stays the same over time, users can have a high degree of confidence that the transactions in that block have not been tampered with. This allows users on the blockchain to determine whether or not they can trust the history of transactions on the blockchain.


  1. United States v. Cartier, 2007 WL 319648, at *1 (D.N.D. Jan. 30, 2007).
  2. NICCS, Explore Terms: A Glossary of Common Cybersecurity Terminology (full-text).


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