> For the complete documentation index, see [llms.txt](https://learn.cypherock.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://learn.cypherock.com/design-decision/pin-protection-on-cypherock-x1.md).

# Pin Protection on Cypherock X1

Cypherock X1 uses an alphanumeric PIN system. Users can choose a PIN between 4 and 8 characters to add an extra layer of protection to each of the 4 wallets created on Cypherock X1. When the PIN is generated, its hash is used to encrypt all 5 cryptographic parts in Cypherock X1.

The double hash of the PIN is stored on each X1 Card and is used to fetch the cryptographic parts stored on the respective X1 Card. When a user enters a PIN on the X1 Vault, the double hash of the PIN is calculated and sent as input to the X1 Card to compare against the stored value on the X1 Card. After successful verification, the cryptographic part is retrieved from the X1 Card.

The X1 Vault has access to the PIN, and its subsequent hash, only for the duration of the session in its RAM. No information about the PIN is permanently stored on the X1 Vault. Whenever a user enters a PIN, it is erased immediately after use.

PIN protection on the X1 Card also includes an exponential time function. A series of incorrect PIN guesses can lock the wallet for up to 100 years.

To learn more about the locking mechanism, refer to Cypherock's [Github page](https://github.com/Cypherock/x1_wallet_firmware/blob/main/docs/cylock__proof_of_work.md) dedicated to the locking mechanism with PIN protection.