Sheet protection stored an internal FNV hash that was never written to
XLSX, and an Excel sheet password was dropped on import, so imported
protected sheets could be unprotected without it. Protect Sheet now
stores a salted SHA-512 hash (spin count 100000) via PasswordHash; the
XLSX sheetProtection password (iterated or legacy) is read and written,
and Unprotect Sheet really verifies it. Hashes from older GridCraft JSON
workbooks are still read and verified.
Refs #346
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
The password fields in Protect Sheet and Unprotect Sheet were plain
text fields, so the password was readable on screen and in the
accessibility tree. A new Password form field masks it as typed and adds
a "Show password" check box that reveals it on purpose (off each time
the dialog opens).
These are the only password fields in the UI: Protect Workbook runs
without a dialog and encrypted files are refused on open.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
