Merge pull request #56 from tong-canonical/reference_cryptography_add_more_info

cryptography.md: add more information about the various cryptographic operations.

Author: SecondSkoll

.wordlist.txt

@@ -29,6 +29,7 @@ LTS
 Makefile
 Matrix
 Mattermost
+microk
 MyST
 namespace
 namespaces

en/cryptography.md

@@ -1,12 +1,28 @@
 # Cryptography
 
 Various Cryptographic technologies are used to enable secure Snap Store Proxy operation.
-Below is an outline of the various functions that use cryptographic technologies,
+Below are the functionalities of the Snap Store Proxy that use cryptographic technologies,
 and the details of the cryptographic technologies used.
 
+- **Signing assertions**: the Snap Store Proxy signs various
+[assertions](https://ubuntu.com/core/docs/reference/assertions).
+The key ID of the signing key is encoded with SHA3-384, and the assertion is signed with RSA.
+
+- **Hash of artefacts**: the Snap Store Proxy generates many hashes of an uploaded artefact
+using SHA3-384, SHA256 and SHA512 to ensure the uniqueness and integrity of the artefact.
+
+- **OCI charm resources credentials**: an OCI runtime
+(e.g. [microk8s](https://microk8s.io/docs)) must authenticate against the Snap Store Proxy
+in order to download the OCI [charm resources](https://juju.is/docs/juju/charm-resource).
+The credentials are encoded as JWT that are signed with RSA.
+
+- **Signing nonce**: A nonce is used as additional security for REST API access.
+RSA is used to sign and verify the nonce.
+
+
 | Function                     | Exposed | Technology               | Package/Library                                                                                                                                                                  |
-|------------------------------|---------|--------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
-| Signing assertions           | Yes     | SHA3-384, RSA 4096/8192  | [snapd](https://github.com/canonical/snapd), [lp-signing](https://launchpad.net/lp-signing)                                                                                      |
-| Hash of artefacts            | Yes     | SHA3-384, SHA256, SHA512 | [review-tools](https://launchpad.net/review-tools)                                                                                                                               |
-| OCI charm resources password | Yes     | RSA 4096, JWT            | [cryptography](https://github.com/pyca/cryptography), [pyjwt](https://github.com/jpadilla/pyjwt), [py-macaroon-bakery](https://github.com/go-macaroon-bakery/py-macaroon-bakery) |
-| Nonce signing                | Yes     | RSA 4096                 | [cryptography](https://github.com/pyca/cryptography), [pem](https://github.com/hynek/pem)                                                                                        |
+|---------------------------------|---------|--------------------------|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
+| Signing assertions              | Yes     | SHA3-384, RSA 4096/8192  | [snapd](https://github.com/canonical/snapd), [lp-signing](https://launchpad.net/lp-signing)                                                                                      |
+| Hash of artefacts               | Yes     | SHA3-384, SHA256, SHA512 | [review-tools](https://launchpad.net/review-tools)                                                                                                                               |
+| OCI charm resources credentials | Yes     | RSA 4096, JWT            | [cryptography](https://github.com/pyca/cryptography), [pyjwt](https://github.com/jpadilla/pyjwt), [py-macaroon-bakery](https://github.com/go-macaroon-bakery/py-macaroon-bakery) |
+| Signing nonce                   | Yes     | RSA 4096                 | [cryptography](https://github.com/pyca/cryptography), [pem](https://github.com/hynek/pem)                                                                                        |