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<ol class="chapter"><li class="chapter-item expanded affix "><a href="../introduction.html">Introduction</a></li><li class="chapter-item expanded "><a href="../quick_start.html"><strong aria-hidden="true">1.</strong> Quick Start</a></li><li class="chapter-item expanded "><a href="../guides/index.html"><strong aria-hidden="true">2.</strong> Guides</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../guides/choose_content_topic.html"><strong aria-hidden="true">2.1.</strong> How to Choose a Content Topic</a></li><li class="chapter-item expanded "><a href="../guides/relay_receive_send_messages.html"><strong aria-hidden="true">2.2.</strong> Receive and Send Messages Using Waku Relay</a></li><li class="chapter-item expanded "><a href="../guides/store_retrieve_messages.html"><strong aria-hidden="true">2.3.</strong> Retrieve Messages Using Waku Store</a></li><li class="chapter-item expanded "><a href="../guides/encrypt_messages_version_1.html" class="active"><strong aria-hidden="true">2.4.</strong> Encrypt Messages Using Waku Message Version 1</a></li><li class="chapter-item expanded "><a href="../guides/reactjs_relay.html"><strong aria-hidden="true">2.5.</strong> Receive and Send Messages Using Waku Relay With ReactJS</a></li><li class="chapter-item expanded "><a href="../guides/reactjs_store.html"><strong aria-hidden="true">2.6.</strong> Retrieve Messages Using Waku Store With ReactJS</a></li><li class="chapter-item expanded "><a href="../guides/light_push_send_messages.html"><strong aria-hidden="true">2.7.</strong> Send Messages Using Waku Light Push</a></li></ol></li><li class="chapter-item expanded "><a href="../examples.html"><strong aria-hidden="true">3.</strong> Examples</a></li><li class="chapter-item expanded affix "><a href="../waku_protocols.html">Implemented Waku Protocols</a></li></ol> </div>
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<h1 id="encrypt-messages-using-waku-message-version-1"><a class="header" href="#encrypt-messages-using-waku-message-version-1">Encrypt Messages Using Waku Message Version 1</a></h1>
<p>The Waku Message format provides an easy way to encrypt messages using symmetric or asymmetric encryption.
The encryption comes with several handy <a href="https://rfc.vac.dev/spec/26/#design-requirements">design requirements</a>:
confidentiality, authenticity and integrity.</p>
<p>You can find more details about Waku Message Payload Encryption in <a href="https://rfc.vac.dev/spec/26/">26/WAKU-PAYLOAD</a>.</p>
<h2 id="what-data-is-encrypted"><a class="header" href="#what-data-is-encrypted">What data is encrypted</a></h2>
<p>With Waku Message Version 1, the entire payload is encrypted.</p>
<p>Which means that the only discriminating data available in clear text is the content topic and timestamp (if present).
Hence, if Alice expects to receive messages under a given content topic, she needs to try to decrypt all messages received on said content topic.</p>
<p>This needs to be kept in mind for scalability and forward secrecy concerns:</p>
<ul>
<li>If there is high traffic on a given content topic then all clients need to process and attempt decryption of all messages with said content topic;</li>
<li>If a content topic is only used by a given (group of) user(s) then it is possible to deduce some information about said user(s) communications such as sent time and frequency of messages.</li>
</ul>
<h2 id="key-management"><a class="header" href="#key-management">Key management</a></h2>
<p>By using Waku Message Version 1, you will need to provide a way to your users to generate and store keys in a secure manner.
Storing, backing up and recovering key is out of the scope of this guide.</p>
<p>If key recovery is important for your dApp, then check out
<a href="https://developer.mozilla.org/en-US/docs/Web/API/SubtleCrypto/wrapKey">SubtleCrypto.wrapKey()</a> which can be used to securely store or export private keys.</p>
<p>An example to save and load a key pair in local storage, protected with a password, can be found in <a href="https://github.com/status-im/js-waku/blob/main/examples/eth-pm/src/key_pair_handling/key_pair_storage.ts">Eth-PM</a>.</p>
<h2 id="which-encryption-method-should-i-use"><a class="header" href="#which-encryption-method-should-i-use">Which encryption method should I use?</a></h2>
<p>Whether you should use symmetric or asymmetric encryption depends on your use case.</p>
<p><strong>Symmetric</strong> encryption is done using a single key to encrypt and decrypt.</p>
<p>Which means that if Alice knows the symmetric key <code>K</code> and uses it to encrypt a message,
she can also use <code>K</code> to decrypt any message encrypted with <code>K</code>,
even if she is not the sender.</p>
<p>Group chats is a possible use case for symmetric encryption:
All participants can use an out-of-band method to agree on a <code>K</code>.
Participants can then use <code>K</code> to encrypt and decrypt messages within the group chat.
Participants MUST keep <code>K</code> secret to ensure that no external party can decrypt the group chat messages.</p>
<p><strong>Asymmetric</strong> encryption is done using a key pair:
the public key is used to encrypt messages,
the matching private key is used to decrypt messages.</p>
<p>For Alice to encrypt a message for Bob, she needs to know Bob's Public Key <code>K</code>.
Bob can then use his private key <code>k</code> to decrypt the message.
As long as Bob keep his private key <code>k</code> secret, then he, and only he, can decrypt messages encrypted with <code>K</code>.</p>
<p>Private 1:1 messaging is a possible use case for asymmetric encryption:
When Alice sends an encrypted message for Bob, only Bob can decrypt it.</p>
<h2 id="symmetric-encryption"><a class="header" href="#symmetric-encryption">Symmetric Encryption</a></h2>
<h3 id="generate-key"><a class="header" href="#generate-key">Generate Key</a></h3>
<p>To use symmetric encryption, you first need to generate a key.
Use <code>generateSymmetricKey</code> for secure key generation:</p>
<pre><code class="language-js">import { generateSymmetricKey } from 'js-waku';
const symmetricKey = generateSymmetricKey();
</code></pre>
<h3 id="encrypt-message"><a class="header" href="#encrypt-message">Encrypt Message</a></h3>
<p>To encrypt a message with the previously generated key,
pass the key in the <code>symKey</code> property to <code>WakuMessage.fromBytes</code>.</p>
<p>Same as Waku Messages version 0 (unencrypted),
<code>payload</code> is your message payload and <code>contentTopic</code> is the content topic for your dApp.
See <a href="./relay_receive_send_messages.html">Receive and Send Messages Using Waku Relay</a> for details.</p>
<pre><code class="language-js">import { WakuMessage } from 'js-waku';
const message = await WakuMessage.fromBytes(payload, contentTopic, {
symKey: symmetricKey
});
</code></pre>
<p>The Waku Message can then be sent to the Waku network using Waku Relay or Waku Light Push:</p>
<pre><code class="language-js">await waku.lightPush.push(message);
</code></pre>
<h3 id="decrypt-messages"><a class="header" href="#decrypt-messages">Decrypt Messages</a></h3>
<p>To decrypt messages,
whether they are received over Waku Relay or using Waku Store,
add the symmetric key as a decryption key to your Waku instance.</p>
<pre><code class="language-js">waku.addDecryptionKey(symmetricKey);
</code></pre>
<p>Alternatively, you can pass the key when creating the instance:</p>
<pre><code class="language-js">import { Waku } from 'js-waku';
const waku = Waku.create({ decryptionKeys: [symmetricKey] });
</code></pre>
<p>It will attempt to decrypt any message it receives using the key, for both symmetric and asymmetric encryption.</p>
<p>You can call <code>addDecryptionKey</code> several times if you are using multiple keys,
symmetric key and asymmetric private keys can be used together.</p>
<p>Messages that are not successfully decrypted are dropped.</p>
<h2 id="asymmetric-encryption"><a class="header" href="#asymmetric-encryption">Asymmetric Encryption</a></h2>
<h3 id="generate-key-pair"><a class="header" href="#generate-key-pair">Generate Key Pair</a></h3>
<p>To use asymmetric encryption, you first need to generate a private key and calculate the corresponding public key.
Use <code>generatePrivateKey</code> for secure key generation:</p>
<pre><code class="language-js">import { generatePrivateKey, getPublicKey } from 'js-waku';
const privateKey = generatePrivateKey();
const publicKey = getPublicKey(privateKey);
</code></pre>
<p>The private key must be securely stored and remain private.
If leaked then other parties may be able to decrypt the user's messages.</p>
<p>The public key is unique for a given private key and can always be recovered given the private key,
hence it is not needed to save it as long as as the private key can be recovered.</p>
<h3 id="encrypt-message-1"><a class="header" href="#encrypt-message-1">Encrypt Message</a></h3>
<p>The public key is used to encrypt messages;
to do so, pass it in the <code>encPublicKey</code> property to <code>WakuMessage.fromBytes</code>.</p>
<p>Same as clear Waku Messages,
<code>payload</code> is your message payload and <code>contentTopic</code> is the content topic for your dApp.
See <a href="./relay_receive_send_messages.html">Receive and Send Messages Using Waku Relay</a> for details.</p>
<pre><code class="language-js">import { WakuMessage } from 'js-waku';
const message = await WakuMessage.fromBytes(payload, contentTopic, {
encPublicKey: publicKey
});
</code></pre>
<p>The Waku Message can then be sent to the Waku network using Waku Relay or Waku Light Push:</p>
<pre><code class="language-js">await waku.lightPush.push(message);
</code></pre>
<h3 id="decrypt-messages-1"><a class="header" href="#decrypt-messages-1">Decrypt Messages</a></h3>
<p>The private key is needed to decrypt messages.</p>
<p>To decrypt messages,
whether they are received over Waku Relay or using Waku Store,
add the private key as a decryption key to your Waku instance.</p>
<pre><code class="language-js">waku.addDecryptionKey(privateKey);
</code></pre>
<p>Alternatively, you can pass the key when creating the instance:</p>
<pre><code class="language-js">import { Waku } from 'js-waku';
const waku = Waku.create({ decryptionKeys: [privateKey] });
</code></pre>
<p>It will attempt to decrypt any message it receives using the key, for both symmetric and asymmetric encryption.</p>
<p>You can call <code>addDecryptionKey</code> several times if you are using multiple keys,
symmetric key and asymmetric private keys can be used together.</p>
<p>Messages that are not successfully decrypted are dropped.</p>
<h2 id="handling-wakumessage-instances"><a class="header" href="#handling-wakumessage-instances">Handling <code>WakuMessage</code> instances</a></h2>
<p>When creating a Waku Message using <code>WakuMessage.fromBytes</code> with an encryption key (symmetric or asymmetric),
the payload gets encrypted.
Which means that <code>wakuMessage.payload</code> returns an encrypted payload:</p>
<pre><code class="language-js">import { WakuMessage } from 'js-waku';
const message = await WakuMessage.fromBytes(payload, contentTopic, {
encPublicKey: publicKey
});
console.log(message.payload); // This is encrypted
</code></pre>
<p>However, <code>WakuMessage</code> instances returned by <code>WakuRelay</code> or <code>WakuStore</code> are always decrypted.</p>
<p><code>WakuRelay</code> and <code>WakuStore</code> never return messages that are encrypted.
If a message was not successfully decrypted, then it will be dropped from the results.</p>
<p>Which means that <code>WakuMessage</code> instances returned by <code>WakuRelay</code> and <code>WakuStore</code> always have a clear payload (in regard to Waku Message version 1):</p>
<pre><code class="language-js">import { Waku } from 'js-waku';
const waku = Waku.create({ decryptionKeys: [privateKey] });
const messages = await waku.store.queryHistory([contentTopic]);
if (messages &amp;&amp; messages[0]) {
console.log(messages[0].payload); // This payload is decrypted
}
waku.relay.addObserver((message) =&gt; {
console.log(message.payload); // This payload is decrypted
}, [contentTopic]);
</code></pre>
<h2 id="code-example"><a class="header" href="#code-example">Code Example</a></h2>
<p>The <a href="https://github.com/status-im/js-waku/tree/main/examples/eth-pm">Eth-PM</a> Web App example demonstrates both the use of symmetric and asymmetric encryption.</p>
<p>Asymmetric encryption is used for private messages so that only the intended recipient can read said messages.</p>
<p>Symmetric encryption is used for the public key messages.
In this instance, the same key is used for all users: the Keccak-256 hash of the content topic (which results in 32 bytes array).
While this does not add functional value, it does demonstrate the usage of symmetric encryption in a web app.</p>
<p>A live version of Eth-PM can be found at https://status-im.github.io/js-waku/eth-pm/.</p>
<p>The specifications of the protocol it implements can be found at <a href="https://rfc.vac.dev/spec/20/">20/TOY-ETH-PM</a>.</p>
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