Add cryptography section

.vscode/settings.json

@@ -1,3 +1,7 @@
 {
-  "cSpell.words": ["Bitwarden"]
+  "cSpell.words": [
+    "Bitwarden"
+  ],
+  "editor.formatOnSave": false,
+  "editor.formatOnPaste": false
 }

docs/contributing/cryptography/_category_.yml

@@ -0,0 +1 @@
+label: "Cryptography"

docs/contributing/cryptography/requirements.md

@@ -0,0 +1,30 @@
+# Requirements
+
+At Bitwarden we protect our users data depending heavily zero-knowledge cryptography. One of the
+most important way of achieving this is by living up to the high standard required from today's and
+tomorrow's cryptography. This document outlines the requirements we have to achieve those goals.
+
+:::info
+For more information about cryptography in Bitwarden, see
+[Bitwarden Security Whitepaper](https://bitwarden.com/help/bitwarden-security-white-paper/)
+:::
+
+## Symmetric encryption
+
+:::info
+All keys used for symmetric encryption should be 512 bits.
+:::
+
+The symmetric encryption
+algorithm used for encrypting vault data is AES-256 in CBC mode. The key size is 256 bits and the IV
+size is 128 bits. The IV is randomly generated for each field and stored along with the cipher text.
+Each operation is accompanied by an HMAC (message authentication code) verification to ensure
+integrity.
+
+The stored symmetric-key object consists of two concatenated keys, one used for encryption and one
+used for HMAC, both 256 bits. This is what we mean when saying that the "`UserKey` is 512 bits".
+
+### Asymmetric encryption
+
+The asymmetric encryption algorithm used for encrypting user data is RSA-2048. The key size is 2048
+bits.