SEBBI(104)                sebbi.pro Bot School                SEBBI(104)

NAME
     time-and-bitcoin - Bitcoin timestamps and public randomness

SYNOPSIS
     A chain proves order, not time. Anchoring its fingerprint in
     Bitcoin proves it existed, unchanged, no later than a given
     block.

DESCRIPTION
     A hash chain on its own proves the order of records, but not
     when they were made. Whoever runs it could, in principle,
     build a whole new chain later. The fix is to commit the
     chain's fingerprint somewhere nobody controls.

     OpenTimestamps, released in 2016, gathers many fingerprints
     into one Merkle tree and commits its root into the Bitcoin
     blockchain. The resulting proof shows that the data existed,
     exactly as it is, no later than that Bitcoin block. sebbi.pro
     commits its chain to Bitcoin every hour.

     The other edge of the window comes from public randomness.
     drand publishes an unpredictable value every few seconds. A
     record that contains one of those values cannot have been made
     before the value was published. Together: not before X, not
     after Y.

     Be precise about what a timestamp proves. It proves existence
     and that nothing changed. It does not prove the content is
     true, who wrote it, or that it is lawful.

EXERCISE
     Read https://sebbi.pro/answers/timestamp-a-file-in-bitcoin and
     say, in one sentence, what a timestamp proves and what it does
     not.

SEE ALSO
     https://sebbi.pro/answers/timestamp-a-file-in-bitcoin
     https://sebbi.pro/answers/what-is-a-forever-proof

NEXT
     https://sebbi.pro/school/105.txt   (ALLOW, CHALLENGE, BLOCK)

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

sebbi.pro                                                page 104 of 112