---
id: KB-SC-008
url: https://app.codecontract.io/help/smartcheck/keeping-proof-for-many-years
idioma: en
categoria: smartcheck
subcategoria: compartir
audiencia: usuario
nivel: avanzado
actualizado: 2026-08-13
tambienEn: [es]
relacionados: [KB-SC-005, KB-TZ-002]
citadoPor: [KB-SC-019, KB-CO-020]
---

# Keeping proof for many years

_What it takes for it to still hold in ten years._

**Responde a:** how long does a seal remain valid · long-term preservation of signed documents · re-sealing old documents · will it still hold in ten years

A seal does not expire with time, but the cryptography behind it ages: what is impossible to forge today may not be in twenty years. For documents that have to last, that needs anticipating.

## What is needed and when

| Document's lifespan | What it needs |
| --- | --- |
| Under 5 years | Nothing special. Keep the file |
| 5 to 15 years | Keep the original file, unconverted |
| Over 15 years | Plus re-sealing before the algorithm becomes obsolete |

## What usually fails is not the cryptography

It is losing the file. Documents that stop being provable after ten years rarely fail on the algorithm: they fail because nobody knows where the file is, or because someone converted it to another format "to archive it better" and thereby changed its fingerprint.

> [!IMPORTANT]
> Converting a sealed file to another format invalidates it as evidence. Keep the original exactly as it was sealed, and if you need a copy in another format, make it an additional copy, not a replacement.

## What to keep, exactly

- The original file, byte for byte.
- The sealing receipt.
- And knowing where both are in ten years, which is the hard part.

> [!NOTE]
> If the document lives on the platform, your retention policy covers this. The problem appears with copies people take to their own drives and later reorganise.

**Am I warned when re-sealing is due?**

Ask about it for your long-lived documents: it is not something to discover late.

**Does re-sealing change the document?**

No. It adds a new layer over the same fingerprint.

**What if I lose the receipt?**

If the document is on the platform, it is recovered. If you only had a loose copy, that is the problem.

## Ejemplos

**An engineering practice keeps projects that may be disputed twenty years later.**

- Keeps the originals unconverted
- Asks about re-sealing for the longest-lived ones

→ The projects remain provable when a claim appears fifteen years on.

**The proof is stored in a format nothing will open in ten years.**

- Keeps the original in a standard format

→ The file stays readable.

**The evidence lives on a machine that gets retired.**

- Stores it off personal machines

→ Migration does not take the proof with it.

**The document is kept and the seal reference is lost.**

- Keeps document and reference together

→ Verification stays possible.

**Systems change and the history is left behind.**

- Includes the proof in the migration plan

→ The evidence survives the change.

**Nobody ever checks whether the proof still verifies.**

- Verifies a sample periodically

→ A problem is found before the proof is needed.