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Add glossary entries and links for chapter 1 - 4 and 6

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Signed-off-by: David Runge <dave@sleepmap.de>
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23
book/source/03-cryptography.md
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@ -16,11 +16,12 @@ Cryptographic hash functions have two important properties:
- [**Pre-image resistance**](https://en.wikipedia.org/wiki/Preimage_attack): Given a hash digest, it should be very difficult to determine any data that matches this hash digest (including, but not limited to, the original data the hash represents). This property embodies the concept of a [one-way function](https://en.wikipedia.org/wiki/One-way_function) – a calculation that is easy to perform, but very hard to reverse.
- [**Collision resistance**](https://en.wikipedia.org/wiki/Collision_resistance): It should be very difficult to find two distinct pieces of data that map to the same hash digest.
(message_authentication_codes)=
## Message authentication codes
A [message authentication code](https://en.wikipedia.org/wiki/Message_authentication_code) (MAC), also known as an authentication tag, is a small piece of information used to verify the integrity and authenticity of a message.
A [message authentication code](https://en.wikipedia.org/wiki/Message_authentication_code) (MAC), also known as an {term}`authentication tag`, is a small piece of information used to verify the integrity and authenticity of a message.
It is derived from the original message using a (symmetric) secret key. The recipient of a message containing a MAC, who is also in possession of the secret key, can verify that the message has not been altered.
It is derived from the original message using a {term}`(symmetric) secret key<Symmetric Secret Key>`. The recipient of a message containing a MAC, who is also in possession of the secret key, can verify that the message has not been altered.
[HMAC](https://en.wikipedia.org/wiki/HMAC) is a type of MAC that relies on a hash function. It is used in the OpenPGP protocol.
@ -33,6 +34,7 @@ A notable KDF for the OpenPGP specification is the [HKDF](https://en.wikipedia.o
For detailed information on KDFs and their role in the OpenPGP protocol, see the [encrypted secrets](encrypted_secrets) chapter and the [SEIPDv2](SEIPDv2) section of the encryption chapter.
(symmetric_key_cryptography)=
## Symmetric-key cryptography
[Symmetric-key cryptography](https://en.wikipedia.org/wiki/Symmetric-key_algorithm) uses the same cryptographic key for both encryption and decryption, unlike asymmetric cryptography where a pair of keys is used: a public key for encryption and a corresponding private key for decryption. Symmetric-key cryptographic systems support *encryption/decryption* operations.
@ -80,6 +82,7 @@ By addressing the malleability problem, AEAD also counters a variation of the EF
[^efail]: A variation of the [EFAIL](https://en.wikipedia.org/wiki/EFAIL) attack can be prevented by both the MDC and AEAD mechanisms. Also see ["No, PGP is not broken, not even with the Efail vulnerabilities,"](https://proton.me/blog/pgp-vulnerability-efail) especially the section "Malleability Gadget Exfiltration Channel Attack."
(public_key_asymmetric_cryptography)=
## Public-key (asymmetric) cryptography
[Public-key cryptography](https://en.wikipedia.org/wiki/Public-key_cryptography) uses asymmetric pairs of related keys. Each pair consists of a public key and a private key. These systems support encryption, decryption, and digital signature operations.
@ -98,9 +101,9 @@ Throughout this document, we will frequently reference asymmetric cryptographic
An asymmetric cryptographic key pair
```
Each key pair comprises two parts: the public key and the private key. For ease of identification in this documentation, the public key will be shown in green and the private key in red. Additionally, public keys are depicted with a solid border and pointing to the right, while private keys are shown with a dotted border and pointing to the left.
Each key pair comprises two parts: the {term}`public key<OpenPGP Certificate>` and the {term}`private key<Transferable Secret Key>`. For ease of identification in this documentation, the {term}`public key<OpenPGP Certificate>` will be shown in green and the private key in red. Additionally, {term}`public keys<OpenPGP Certificate>` are depicted with a solid border and pointing to the right, while {term}`private keys<Transferable Secret Key>` are shown with a dotted border and pointing to the left.
It's important to note that in many scenarios, only the public key is exposed or used. These situations will be elaborated upon in subsequent sections of this document.
It's important to note that in many scenarios, only the {term}`public key<OpenPGP Certificate>` is exposed or used. These situations will be elaborated upon in subsequent sections of this document.
```{figure} diag/public_key.png
:name: fig-public-key
@ -111,7 +114,7 @@ The public part of an asymmetric key pair
### Usage and terminology in OpenPGP
OpenPGP extensively uses public-key cryptography for encryption and digital signing operations.
OpenPGP extensively uses {term}`public-key cryptography<Public Key Algorithm>` for encryption and digital signing operations.
```{admonition} Terminology
:class: note
@ -123,11 +126,11 @@ While "secret key" (as used in the OpenPGP RFC) and "private key" serve the same
### Cryptographic digital signatures
[Digital signatures](https://en.wikipedia.org/wiki/Digital_signature) are a fundamental mechanism of asymmetric cryptography, providing secure, mathematical means to validate the authenticity, integrity, and origin of digital messages and documents.
[Digital signatures](https://en.wikipedia.org/wiki/Digital_signature) are a fundamental mechanism of {term}`asymmetric cryptography`, providing secure, mathematical means to validate the {term}`authenticity<Authentication>`, integrity, and origin of digital messages and documents.
In OpenPGP, digital signatures have diverse applications, extending beyond mere validation of a message's origin. They can signify various intents, including certification, consent, acknowledgment, or even revocation by the signer. The multifaceted nature of "statements" conveyed through digital signatures in cryptographic protocols is wide-ranging but crucial, allowing third parties to inspect/evaluate these statements for authenticity and intended purpose.
In OpenPGP, digital signatures have diverse applications, extending beyond mere validation of a message's origin. They can signify various intents, including {term}`certification`, consent, acknowledgment, or even revocation by the signer. The multifaceted nature of "statements" conveyed through {term}`digital signatures<OpenPGP Signature Packet>` in cryptographic protocols is wide-ranging but crucial, allowing third parties to inspect/evaluate these statements for {term}`authenticity<Authentication>` and intended purpose.
Digital signatures in OpenPGP are used in two primary contexts:
{term}`Digital signatures<OpenPGP Signature Packet>` in OpenPGP are used in two primary contexts:
- [Data signatures](signing_data)
- [Signatures on components](component_signatures_chapter)
@ -135,8 +138,8 @@ Digital signatures in OpenPGP are used in two primary contexts:
(hybrid_cryptosystems)=
## Hybrid cryptosystems
[Hybrid cryptosystems](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) combine the use of symmetric and asymmetric (public-key) cryptography to capitalize on the strengths of each, namely symmetric cryptography's speed and efficiency and public-key cryptography's mechanism for secure key exchange.
[Hybrid cryptosystems](https://en.wikipedia.org/wiki/Hybrid_cryptosystem) combine the use of {term}`symmetric<Symmetric Cryptography>` and {term}`asymmetric (public-key)<Asymmetric Cryptography>` cryptography to capitalize on the strengths of each, namely {term}`symmetric cryptography`'s speed and efficiency and {term}`public-key cryptography<Asymmetric Cryptography>`'s mechanism for secure key exchange.
### Usage and terminology in OpenPGP
OpenPGP uses a hybrid cryptosystem for encryption. This approach involves generating unique shared secrets, known as "session keys," for each session. For detailed information on this topic, please refer to the chapters {ref}`encryption_chapter` and {ref}`decryption_chapter`.
OpenPGP uses a {term}`hybrid cryptosystem` for encryption. This approach involves generating unique shared secrets, known as "session keys," for each session. For detailed information on this topic, please refer to the chapters {ref}`encryption_chapter` and {ref}`decryption_chapter`.