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Link to algorithm-specific session key encryption sections

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Paul Schaub 2023-12-08 15:43:03 +01:00 • committed by Heiko Schaefer
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book/source/11-decryption.md
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@ -85,13 +85,13 @@ Here, the recipients secret key is used to decrypt the session-key.
With version 3 PKESKs, the recipients secret encryption (sub-) key is directly used to decrypt the encrypted *session key*.
The key ID of the subkey to be used is recorded in the PKESKs key-id field. A value of `0` indicates an anonymous recipient (see [](decryption_anonymous_recipient)).
To detect, which symmetric cipher is used to decrypt the SEIPDv1 packet later on, each public key algorithm uses a slightly different encoding to unpack the symmetric algorithm tag from the decrypted session key. See sections 5.1.3 through 5.1.7 of the OpenPGP specification. Typically, the cipher algorithm ID is prefixed the the actual session key.
To detect, which symmetric cipher is used to decrypt the SEIPDv1 packet later on, each public key algorithm uses a slightly different encoding to unpack the symmetric algorithm tag from the decrypted session key. See the respective sections[^rsa-spec] [^elgamal-spec] [^ecdh-spec] [^x25519-spec] [^x448-spec] of the standard. Typically, the cipher algorithm ID is prefixed the the actual session key.
```{admonition} TODO
:class: warning
Link those sections directly
```
[^rsa-spec]: [Algorithm-Specific Fields for RSA encryption](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-algorithm-specific-fields-f)
[^elgamal-spec]: [Algorithm-Specific Fields for Elgamal encryption](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-algorithm-specific-fields-fo)
[^ecdh-spec]: [Algorithm-Specific Fields for ECDH encryption](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-algorithm-specific-fields-for)
[^x25519-spec]: [Algorithm-Specific Fields for X25519 encryption](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-algorithm-specific-fields-for-)
[^x448-spec]: [Algorithm-Specific Fields for X448 encryption](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-12.html#name-algorithm-specific-fields-for-x)
```{figure} drawio/PKESKv3-decryption.svg
:name: fig-decryption-pkesk3