MSC3892: Custom Emotes with Encryption

proposals/3892-custom-emotes-with-encryption.md

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+# MSC3892: Emotes
+## Proposal
+#### Definitions:
+Emotes: Short for emoticons, a shortcode/image pair that are used inline in messages and in reactions. <br/> 
+Emojis: Shortcode/image pairs with unicode representations. Currently supported in most clients. A subset of emotes. <br/> 
+Shortcode: A short piece of text surrounded in colons to represent an emote/emoji. Ex. :shortcode: 
+<br/><br/>
+Every emote proposal uses a shortcode and a way to store the image and make the client render it. <br/> 
+Under this proposal they are not sent in the message source as img tags, which is what many non-Element clients use. <br/> 
+In this proposal, the message source is not edited and it is sent as a shortcode. Rather, it is up to the client to <br/>load it when rendering messages.<br/> 
+<br/><br/>
+In the current implementation/proposal it is rendered in the message html as follows:
+
+```html
+ <img class="mx_Emote" title=":shortcode:" src="blob:https://example.com/blob-guid">
+```
+This is similar to current implementations in structure, but rather than having clients render img tags <br/>
+from the message source they are added during construction of the message html. Encrypted rooms can use the blob obtained after decryption
+while unencrypted ones can directly use the mxc url.
+
+## Emote sources
+### Room emotes
+Room emotes are per-room emotes that are defined in an m.room.emotes event. They can be uploaded from the room settings by moderators or above.
+The emotes are defined inside of a dict which has the shortcode as a key and the either encrypted or unencrypted source for the emote as a value.
+### Storage format
+For encrypted rooms the m.room.emotes event follows the format:
+```
+{
+"content":{
+	"short": IEncryptedFile (a json object with information on how to decrypt the file)
+	}
+}
+```
+
+For non encrypted rooms the m.room.emotes event follows: 
+```
+{
+"content":{
+ 	"short": “mxc://abcdefg”
+	}
+}
+```
+
+Note: this format could be modified, but would have to be agreed upon so the clients can load the emotes in properly.
+
+## Alternatives:
+Other proposals regarding this issue: [MSC2545](https://github.com/matrix-org/matrix-spec-proposals/pull/2545) and [MSC1951](https://github.com/matrix-org/matrix-doc/pull/1951)
+
+Below is a comparison highlighting the differences between this and other proposals.
+### Advantages
+#### Security
+Emotes in private rooms can be encrypted so that potentially sensitive data is not publicly available to server members. <br/> 
+Emotes in public rooms are necessarily unencrypted. <br/>
+One important note is that although emotes are encrypted they are available to anyone in the private room, and server <br/> 
+admins can see the emotes in the room state so they are not e2ee like messages. <br/> 
+If the file keys or room state is encrypted [MSC3414](https://github.com/matrix-org/matrix-spec-proposals/pull/3414) and if server admins lose the ability to join any private room <br/>it would then be e2ee.
+The current advantage is that the emotes will not be obtainable for other users on the server who are not in the private room.
+<br/>
+#### Message source is not edited
+The client does not edit the actual sent message but renders emotes locally. Leaving the message source untouched <br/>
+ could be helpful for future updates or deleting emotes/changing the way emotes are rendered.
+<br/>
+#### Rendering
+Current implementations use data-mx-emoticon types in the img tag. This uses the mx_Emote class name although that <br/>
+could also be changed since it is rendered locally.
+Compatibility with other MSCs: Although certain aspects of other MSCs cannot be kept the same, many general ideas from <br/>
+those could be carried over.
+### Disadvantages
+#### Lack of user-specific emotes. 
+It might be possible to implement this in public rooms if the client pulls every user’s public emote data to load. <br/>
+Generally, however, user specific emotes goes against the idea of emotes being a shared set of images. <br/>
+Additionally, user specific emotes could be handled by sending image data in the message json, but that would be <br/>
+separate from room emotes as defined in this proposal since room emotes should update when the room settings are updated.
+
+#### Might be more difficult for clients to implement
+Requires existing clients to change their implementations.
+## Additional Points
+This could be extended to spaces although the main current implementation does not have this. <br/>
+Spaces would take priority over individual room emotes if there is a shortcode clash. 
+<br/><br/>
+Add custom emotes for reactions and the emoji picker. 
+<br/><br/>
+Other MSCs introduced the idea of shareable packs. This could be compatible with image packs except for encrypted rooms. <br/> 
+It would be simpler to allow users to download a zip file of all the emotes in a room.
+<br/><br/>