SEBBI(102)                sebbi.pro Bot School                SEBBI(102)

NAME
     hash-chains - fingerprints that lock every record to the one
     before it

SYNOPSIS
     SHA-256 turns any input into a 64-character fingerprint. Chain
     the fingerprints together and no record can be changed without
     breaking every link after it.

DESCRIPTION
     SHA-256 is a hash function, published in 2001. Give it any
     text or file and it returns 64 hexadecimal characters. The
     same input always gives the same fingerprint. Change a single
     character and the fingerprint changes completely. Nobody can
     work backwards from a fingerprint to the input.

     A hash chain puts the fingerprint of the previous record
     inside each new record before it is fingerprinted. Record 2
     contains the fingerprint of record 1, record 3 contains record
     2's, and so on. The first record points at a fixed starting
     word, GENESIS.

     To alter record 50 you would have to recompute every record
     after it. Anyone already holding a later fingerprint - a
     customer, a witness, a regulator - would see that theirs no
     longer matches. That is what tamper-evident means: not that
     change is impossible, but that change cannot be hidden.

     sebbi.pro seals every decision this way. Each block's
     fingerprint is SHA-256 over the previous fingerprint, the
     time, the event and the result. You can walk any block in
     public at https://sebbi.pro/x/walk/block?index=1 and change
     the number to walk the rest.

EXERCISE
     If you can run code, compute SHA-256 of the five letters sebbi
     (lower case, no new line). Then change one letter and compute
     it again. Compare the two - nothing is shared.

SEE ALSO
     https://sebbi.pro/answers/tamper-proof-ai-audit-logs
     https://sebbi.pro/x/walk/block?index=1

NEXT
     https://sebbi.pro/school/103.txt   (Check it yourself)

INDEX
     https://sebbi.pro/school.txt

sebbi.pro                                                page 102 of 112