Improving the Proof of Sats card sealing process

On some of the first Proof of Sats cards produced, we identified a slight lifting along one edge of the seal protecting the card’s private key.

This did not affect the confidentiality of the private key: it remained hidden beneath the opaque seal, and any attempt to access it would have visibly altered the VOID security label.

However, a Proof of Sats card is designed as a collectible object intended to be preserved over time. Even a minor visual defect on the seal can create doubt about its integrity, particularly after long-term storage or in the event of a future resale.

We therefore decided to revise our manufacturing process.

A new sealing process

The issue came from the way the paper insert containing the private key QR code was positioned beneath the security label.

In the original version, this insert was folded. Although the pressure involved was limited, the fold could create permanent mechanical stress beneath the seal and, in some cases, cause one edge to lift slightly.

The new process introduces several changes:

• a more compact QR code;
• a smaller insert;
• a completely flat, non-folded assembly.

This removes the mechanical stress caused by the fold while maintaining a large adhesive surface around the insert (70%).

Validating the new assembly

Several prototypes were produced and subjected to accelerated temperature tests, including 12 hours at -11°C and 12 hours at 60°C.

No lifting was observed during these tests.

These tests allowed us to compare the different configurations and validate the new process before putting it into production.

All new Proof of Sats cards are now assembled using this method.

What about Series 1 cards that were already assembled?

For Series 1 cards still in our possession, the original setup is replaced with the new process before the cards are offered for sale.

When a card had already been sealed, the original seal is opened and the private key stored on its physical insert is temporarily re-entered into the production workstation in order to generate the new insert. A new VOID security seal is then applied.

No digital files containing private keys are retained once the process is complete.

For the first collectors

Several options are being offered to buyers of the first cards potentially affected:

• a full refund, including return shipping costs;
• returning the card so that the sealing system can be replaced;
• keeping the card with its original sealing process, documented through a production note on its Verify page, together with a free card using the new sealing process.

Our goal is to allow each collector to choose the solution that suits them best.

Continuing to improve Proof of Sats

Proof of Sats is a project that combines a fully digital asset with a physical object designed to be preserved over time.

This creates specific challenges in terms of manufacturing, security and long-term preservation.

Series 1 is now available with the new sealing system.

Thank you to our first collectors for their support and trust.

Proof of Sats
Bitcoin history, made collectible.