openpgp-notes/book/source/10-encryption.md

(encryption_chapter)=
# Encryption

[Encryption](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#section-2.1) is one of the core facilities of OpenPGP. It provides confidentiality.

## High-Level overview of the message encryption process

Core concept:

- The plaintext is encrypted with a symmetric "session key."
- The "session key" itself is stored in encrypted form, possibly multiple times:
  - The session key is encrypted to the encryption keys of each intended recipient of the message.
  - Alternatively, or additionally, the session key may be encrypted using a passphrase (this mode of operation doesn't require any OpenPGP certificates.)

## Generations of encryption

### SEIPD w/ AEAD (v2)

### SEIPD (v1)

### SED

## Advanced topics

### Encrypt for multiple/single subkey per certificate?

### "Negotiating" algorithms based on recipients preference subpackets

#### Prevent "downgrade" -> Policy

### Implications of how a recipient cert is "addressed" (fingerprint/key-ID vs. user-ID) (preferences, expiration, revocation)

## Zooming in: Packet structure

### Encryption yields a 'wrapped' openpgp packet stream

### SKESK

Also see https://flowcrypt.com/docs/guide/send-and-receive/send-password-protected.html
Edits in chapter two; add link anchors to point to 2023-09-20 14:48:26 +02:00			`(encryption_chapter)=`
Initial outline and old notes (Rough merge of two precursor projects by Heiko, and outline notes by Paul) 2023-09-14 21:30:43 +02:00			`# Encryption`

ch10: outline 2023-09-25 16:43:36 +02:00			`[Encryption](https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-10.html#section-2.1) is one of the core facilities of OpenPGP. It provides confidentiality.`

			`## High-Level overview of the message encryption process`

			`Core concept:`

			`- The plaintext is encrypted with a symmetric "session key."`
			`- The "session key" itself is stored in encrypted form, possibly multiple times:`
			`- The session key is encrypted to the encryption keys of each intended recipient of the message.`
			`- Alternatively, or additionally, the session key may be encrypted using a passphrase (this mode of operation doesn't require any OpenPGP certificates.)`

			`## Generations of encryption`

			`### SEIPD w/ AEAD (v2)`

			`### SEIPD (v1)`

			`### SED`

			`## Advanced topics`

			`### Encrypt for multiple/single subkey per certificate?`

			`### "Negotiating" algorithms based on recipients preference subpackets`

			`#### Prevent "downgrade" -> Policy`

			`### Implications of how a recipient cert is "addressed" (fingerprint/key-ID vs. user-ID) (preferences, expiration, revocation)`

fix/normalize "zooming in" section titles 2023-10-03 20:07:55 +02:00			`## Zooming in: Packet structure`
Note about SKESK use by flowcrypt 2023-09-28 16:02:47 +02:00
			`### Encryption yields a 'wrapped' openpgp packet stream`

			`### SKESK`

			`Also see https://flowcrypt.com/docs/guide/send-and-receive/send-password-protected.html`