The same lines, sealed and changed
The workshop’s lathe is in bay 2.
The lathe’s manual is on the shelf beside it.
The hall’s schedule changes on Mondays.
Still the same
the workshop’s lathe is in bay 2.
The lathe’s manual is on the shelf beside it.
The hall’s schedule changes on Mondays.
Something changed
How it works
A program works out a code from everything between the cover line and the seal. That code, written at the end, is the seal.
Later, a program works out the code again from the same part of the file. If the two codes match, nothing in that part changed.
Change one letter, and the new code comes out different.
Here is a tiny version to try by hand. Give each letter a number, add them all up, and keep the last two digits.
Change one letter and that total changes too. The real method is much longer, and it is public, so anyone can run it and get the same code.
What it does not show
The seal shows that something changed. It does not show who sealed the pack, or whether a statement inside is true.
A pack with a mistake in it can carry a seal that matches.
Sapphire is software rooted in meaning: what’s said, from where, and how it fits together. Lines marked ‘Sapphire’ are hers.
The seal covers every part after the cover line and before the seal itself. The cover line sits outside it.
Source: The pack rules · section 6