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judymcconville@roadrunner.com 2017-05-03 10:04:03 -07:00
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@ -416,7 +416,7 @@ With all the other fields filled, the block header is now complete and the proce
==== Proof-of-Work Algorithm
((("mining and consensus", "mining the block", "Proof-of-Work algorithm")))((("Proof-of-Work algorithm", id="proof10")))((("mining and consensus", "Proof-of-Work algorithm", id="Cproof10")))A hash algorithm takes an arbitrary-length data input and produces a fixed-length deterministic result, a digital fingerprint of the input. For any specific input, the resulting hash will always be the same and can be easily calculated and verified by anyone implementing the same hash algorithm. ((("collisions")))The key characteristic of a cryptographic hash algorithm is that it is computationally infeasible to find two different inputs that produce the same fingerprint (known as a _collision_). As a corollary, it is also virtually impossible to select an input in such a way as to produce a desired fingerprint, other than trying random inputs.
((("Proof-of-Work algorithm", id="proof10")))((("mining and consensus", "Proof-of-Work algorithm", id="Cproof10")))A hash algorithm takes an arbitrary-length data input and produces a fixed-length deterministic result, a digital fingerprint of the input. For any specific input, the resulting hash will always be the same and can be easily calculated and verified by anyone implementing the same hash algorithm. ((("collisions")))The key characteristic of a cryptographic hash algorithm is that it is computationally infeasible to find two different inputs that produce the same fingerprint (known as a _collision_). As a corollary, it is also virtually impossible to select an input in such a way as to produce a desired fingerprint, other than trying random inputs.
With SHA256, the output is always 256 bits long, regardless of the size of the input. In <<sha256_example1>>, we will use the Python interpreter to calculate the SHA256 hash of the phrase, "I am Satoshi Nakamoto."