(private_key_chapter)=
# Private keys

```{admonition} TODO
:class: warning

- Consistently consider private key material as a separate thing from Certificates? (like in pkcs#11?)
```

## Transferable secret keys

https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#name-transferable-secret-keys


(encrypted_secrets)=
## Password protecting secret key material

```{admonition} TODO
:class: warning

S2K, symmetric encryption
```


## Private key operations

The core of private key operations doesn't require access to the whole certificate. A private key subsystem only needs to handle the cryptographic key material.

### OpenPGP card for private keys

[OpenPGP card](https://en.wikipedia.org/wiki/OpenPGP_card) devices are a type of hardware security device. They are one popular way to handle OpenPGP private key material. These devices do not store the full OpenPGP certificate.

## Advanced topics

### TSKs: Best practices S2K + S2K migration?

### The KOpenPGP attack