Sign formulas

Record that a reviewer has checked a cell or a block of formulas. Signing appends a tamper-evident attestation to the ledger; it is evidence of review, not a guarantee of correctness.

These are reviewer attestations, not cryptographic signatures

“Sign” here means a named reviewer attested to a cell or block, recorded in the SHA-256 hash-chained ledger. The reviewer is identified by a name string (no cryptographic identity), and this is not an Authenticode or public-key signature. It proves a review happened and is tamper-evident — it does not prove the formula is correct or that the reviewer had authority.

Sign Cell

What it does

Appends a ReviewerSigned record for the selected cell, capturing the formula (or a value preview for constants), the signer’s name (pre-filled from Windows), an optional claim, and optional notes.

Steps

  1. Select the cell you have reviewed.
  2. ModelXcel Pro → Proof → Sign Cell.
  3. Confirm the signer, add a claim/notes, and sign. (For a constant, the dialog notes that you are attesting the value.)

Sign Block

What it does

Signs a contiguous rectangular range whose cells all share one master FormulaR1C1 — the common case of a formula copied across a row or column. The signature records the scope and the master formula.

What defines a block (and what breaks it)

  • Every cell in the range must carry a formula equal to the master, compared exactly (ordinal). If any cell is blank or diverges, signing is refused and the offending cell is named.
  • After signing, a hardcoded plug (a constant where a formula was) or an R1C1 divergence breaks the block — detected by Verify Workbook, which appends a BlockBroken counter-record.

What it records

A BlockSigned record with the scope (top-left/bottom-right, rows, columns, orientation), the master FormulaR1C1, and a SHA-256 signature hash over the scope, master, and variant set.

What signing does and does not establish

Signing proves a named reviewer attested at that moment and that a block’s cells shared one formula then; the ledger makes later tampering or divergence detectable. It does not prove the formula is correct, that inputs are trustworthy, that outputs are accurate, or that the reviewer had authority — and it does not lock the cells. See What proof proves — and what it doesn’t.