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50 lines
1.5 KiB
Markdown
50 lines
1.5 KiB
Markdown
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SPDX-FileCopyrightText: 2023 The "Notes on OpenPGP" project
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SPDX-License-Identifier: CC-BY-SA-4.0
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-->
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(encryption_chapter)=
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# Encryption
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[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.
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## High-Level overview of the message encryption process
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Core concept:
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- The plaintext is encrypted with a symmetric "session key."
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- The "session key" itself is stored in encrypted form, possibly multiple times:
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- The session key is encrypted to the encryption keys of each intended recipient of the message.
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- Alternatively, or additionally, the session key may be encrypted using a passphrase (this mode of operation doesn't require any OpenPGP certificates.)
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## Generations of encryption
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### SEIPD w/ AEAD (v2)
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### SEIPD (v1)
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## Advanced topics
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### Encrypt for multiple/single subkey per certificate?
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### "Negotiating" algorithms based on recipients preference subpackets
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#### Prevent "downgrade" -> Policy
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### Implications of how a recipient cert is "addressed" (fingerprint/key-ID vs. user-ID) (preferences, expiration, revocation)
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### AEAD modes: GCM
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```{admonition} TODO
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:class: warning
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Produce text around discussion: https://mailarchive.ietf.org/arch/msg/openpgp/ZTYD5VJsG1k2jJBbn5zIAf5o7d4/
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```
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## Zooming in: Packet structure
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### Encryption yields a 'wrapped' openpgp packet stream
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### SKESK
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Also see https://flowcrypt.com/docs/guide/send-and-receive/send-password-protected-emails.html
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