doc: add readme for @waku/message-encryption

packages/message-encryption/README.md

@@ -0,0 +1,65 @@
+# `@waku/message-encryption`
+
+Provide Waku Message Version 1 payload encryption as defined in [26/WAKU2-PAYLOAD](https://rfc.vac.dev/spec/26/).
+
+## Symmetric Encryption
+
+Symmetric encryption uses a unique key to encrypt and decrypt messages.
+
+```typescript
+import {
+  createDecoder,
+  createEncoder,
+  generateSymmetricKey,
+} from "@waku/message-encryption/symmetric";
+
+// Generate a random key
+const key = generateSymmetricKey();
+
+// To send messages, create an encoder
+const encoder = createEncoder(contentTopic, key);
+
+// For example
+waku.lightPush.push(encoder, { payload });
+
+// To receive messages, create a decoder
+const decoder = createDecoder(contentTopic, key);
+
+// For example
+await waku.store.queryOrderedCallback([decoder], (msg) => {
+  // ...
+});
+```
+
+## ECIES Encryption
+
+ECIES encryption enables encryption for a public key and decryption using a private key.
+
+```typescript
+import {
+  createDecoder,
+  createEncoder,
+  generatePrivateKey,
+  getPublicKey,
+} from "@waku/message-encryption/ecies";
+
+// Generate a random private key
+const privateKey = generatePrivateKey();
+
+// Keep the private key secure, provide the public key to the sender
+const publicKey = getPublicKey(privateKey);
+
+// To send messages, create an encoder
+const encoder = createEncoder(contentTopic, publicKey);
+
+// For example
+waku.lightPush.push(encoder, { payload });
+
+// To receive messages, create a decoder
+const decoder = createDecoder(contentTopic, privateKey);
+
+// For example
+await waku.store.queryOrderedCallback([decoder], (msg) => {
+  // ...
+});
+```