>>310793695
https://en.wikipedia.org/wiki/Cryptographic_hash_function
https://en.wikipedia.org/wiki/Secure_Hash_Algorithms
here's an example use case
>have some file
>want to share file with friend but ur worried the NSA might intercept your file and edit it to include spyware
>run your file through a hash function
>hash function takes all of the contents of the file (as in bits) and spits out some result in a form of a string (e.g. 730e109bd7a8a32b1cb9d9a09aa2325d2430587ddbc0c38bad911525)
>send file to friend
>friend runs the same hash function on the file he received
>if he gets the same result then it's clear he received the same exact file you sent him, without it being altered in any way