feat: encrypted chat

[agazso]

This is a breaking change

Basic encrypted chat. When sharing an invite link the public key is shared instead of the address, therefore it is possible to create a shared secret with ECDH that is used as a symmetric encryption key. The waku topic is the hash of a value derived from the symmetric encryption key. The localStorage is also encrypted, both the keys and the values.

Known issues:

• The chat id is the actual encryption key and it is used in the URL for both private chats and group chats. Therefore if someone takes a picture of the screen may be able to decrypt a conversation. This can be fixed by using a different value derived from the chat id in the URL.
• The invite messages are put in a special topic derived from the invited user's public key and they are encrypted, but they are encrypted with a key derived from the invited user's public key. So if you know someone then you can see who invites them to a chat (but not the actuals conversations, because that is encrypted with the ECDH shared secret). This can be fixed by using ECIES with an ephemeral public key for the invites so that only the invitee can see the actual invite messages.
• The messages are currently not signed, so in a group chat it is possible to impersonate others. The fix could be to use signing for the messages.

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
waku-objects-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 7, 2023 11:47am

[vojtechsimetka]

I tried it and it works quite well! I found two things that broke:

• when someone starts chatting with me (private chat), I am no longer redirected from the invite page to the chat
• If i already have private a chat with someone and I past the invite link, I am not redirected to that chat. Instead I see the invite screen with options Start new chat and Decline

[vojtechsimetka]

Nice addition!

[vojtechsimetka]

I think this would be cleaner as single function that takes both Uint8Array and Hex types. It would make it easier to use in code.

Suggested change

	export function hash(data: Uint8Array): Hex {
	const hashBytes = keccak_256(data)
	return bytesToHex(hashBytes)
	}
	export function hashHex(data: Hex): Hex {
	const bytes = hexToBytes(data)
	return hash(bytes)
	}
	export function hash(data: Hex | Uint8Array): Hex {
	const bytes = typeof data === 'string' ? hexToBytes(data) | data
	const hashBytes = keccak_256(data)
	return bytesToHex(hashBytes)
	}

[agazso]

I tried it and it works quite well! I found two things that broke:

* when someone starts chatting with me (private chat), I am no longer redirected from the invite page to the chat

* If i already have private a chat with someone and I past the invite link, I am not redirected to that chat. Instead I see the invite screen with options `Start new chat` and `Decline`

I fixed the second one.

Regarding the first one, there is only a redirect if you are on the invite page (e.g. showing your QR code) otherwise it could be bad UX if the app would just redirect when you are typing in a different chat. On the invite page it is working for me, can you please check if it is working for you?

[vojtechsimetka]

Yes it works now, I get this screen as the person who is inviting someone once the chat is created.

[filoozom]

This will not work with external wallets like MetaMask. Not necessarily a huge problem, but good to keep in mind in case we want to support these at some point.

Also, what's the point of encrypting the localStorage if you can just get the wallet's private key and decrypt it anyways? Or where is the wallet stored?

[agazso]

Good point regarding external wallets.

When you disconnect the mnemonic is deleted from the localstorage, but your other data is not. This way if you are paranoid you can use the app by connecting with your mnemonic and disconnecting when you are done, but your data may stay in the localstorage and you can still keep you contacts etc. Or you can have multiple accounts and change between them easily.

The alternative would be to delete everything from the localstorage when you disconnect, but that would make multiple accounts less convenient, so I choose to use encryption instead.