diff --git a/src/activitypub/actors.js b/src/activitypub/actors.js
index 917efa4531..5a67012c22 100644
--- a/src/activitypub/actors.js
+++ b/src/activitypub/actors.js
@@ -30,13 +30,13 @@ Actors.assert = async (ids, options = {}) => {
 
 	const actors = await Promise.all(ids.map(async (id) => {
 		try {
-			const actor = (typeof id === 'object' && id.hasOwnProperty('id')) ? id : await activitypub.get(0, id);
+			const actor = (typeof id === 'object' && id.hasOwnProperty('id')) ? id : await activitypub.get('uid', 0, id);
 
 			// Follow counts
 			try {
 				const [followers, following] = await Promise.all([
-					actor.followers ? activitypub.get(0, actor.followers) : { totalItems: 0 },
-					actor.following ? activitypub.get(0, actor.following) : { totalItems: 0 },
+					actor.followers ? activitypub.get('uid', 0, actor.followers) : { totalItems: 0 },
+					actor.following ? activitypub.get('uid', 0, actor.following) : { totalItems: 0 },
 				]);
 				actor.followerCount = followers.totalItems;
 				actor.followingCount = following.totalItems;
@@ -46,7 +46,7 @@ Actors.assert = async (ids, options = {}) => {
 			}
 
 			// Post count
-			const outbox = actor.outbox ? await activitypub.get(0, actor.outbox) : { totalItems: 0 };
+			const outbox = actor.outbox ? await activitypub.get('uid', 0, actor.outbox) : { totalItems: 0 };
 			actor.postcount = outbox.totalItems;
 
 			return actor;
diff --git a/src/activitypub/helpers.js b/src/activitypub/helpers.js
index 7cc91f97ad..49f42dba31 100644
--- a/src/activitypub/helpers.js
+++ b/src/activitypub/helpers.js
@@ -63,8 +63,8 @@ Helpers.query = async (id) => {
 	return { username, hostname, actorUri, publicKey };
 };
 
-Helpers.generateKeys = async (uid) => {
-	winston.verbose(`[activitypub] Generating RSA key-pair for uid ${uid}`);
+Helpers.generateKeys = async (type, id) => {
+	winston.verbose(`[activitypub] Generating RSA key-pair for ${type} ${id}`);
 	const {
 		publicKey,
 		privateKey,
@@ -80,47 +80,41 @@ Helpers.generateKeys = async (uid) => {
 		},
 	});
 
-	await db.setObject(`uid:${uid}:keys`, { publicKey, privateKey });
+	await db.setObject(`${type}:${id}:keys`, { publicKey, privateKey });
 	return { publicKey, privateKey };
 };
 
-Helpers.resolveLocalUid = async (input) => {
-	let slug;
-	const protocols = ['https'];
-	if (process.env.CI === 'true') {
-		protocols.push('http');
-	}
+Helpers.resolveLocalId = async (input) => {
 	if (Helpers.isUri(input)) {
 		const { host, pathname } = new URL(input);
 
 		if (host === nconf.get('url_parsed').host) {
-			const [type, value] = pathname.replace(nconf.get('relative_path'), '').split('/').filter(Boolean);
-			if (type === 'uid') {
-				return value;
+			const [prefix, value] = pathname.replace(nconf.get('relative_path'), '').split('/').filter(Boolean);
+
+			switch (prefix) {
+				case 'uid':
+					return { type: 'user', id: value };
+
+				case 'post':
+					return { type: 'post', id: value };
+
+				case 'category':
+					return { type: 'category', id: value };
+
+				case 'user': {
+					const uid = await user.getUidByUserslug(value);
+					return { type: 'user', id: uid };
+				}
 			}
 
-			slug = value;
+			throw new Error('[[error:activitypub.invalid-id]]');
 		} else {
 			throw new Error('[[error:activitypub.invalid-id]]');
 		}
 	} else if (input.indexOf('@') !== -1) { // Webfinger
-		([slug] = input.replace(/^acct:/, '').split('@'));
-	} else {
-		throw new Error('[[error:activitypub.invalid-id]]');
-	}
-
-	return await user.getUidByUserslug(slug);
-};
-
-Helpers.resolveLocalPid = async (uri) => {
-	const { host, pathname } = new URL(uri);
-	if (host === nconf.get('url_parsed').host) {
-		const [type, value] = pathname.replace(nconf.get('relative_path'), '').split('/').filter(Boolean);
-		if (type !== 'post') {
-			throw new Error('[[error:activitypub.invalid-id]]');
-		}
-
-		return value;
+		const [slug] = input.replace(/^acct:/, '').split('@');
+		const uid = await user.getUidByUserslug(slug);
+		return { type: 'user', id: uid };
 	}
 
 	throw new Error('[[error:activitypub.invalid-id]]');
diff --git a/src/activitypub/inbox.js b/src/activitypub/inbox.js
index a4928a1caa..c2d1d60247 100644
--- a/src/activitypub/inbox.js
+++ b/src/activitypub/inbox.js
@@ -5,6 +5,7 @@ const winston = require('winston');
 const db = require('../database');
 const user = require('../user');
 const posts = require('../posts');
+const categories = require('../categories');
 const activitypub = require('.');
 
 const helpers = require('./helpers');
@@ -56,16 +57,19 @@ inbox.update = async (req) => {
 
 inbox.like = async (req) => {
 	const { actor, object } = req.body;
-	const pid = await activitypub.helpers.resolveLocalPid(object);
+	const { type, id } = await activitypub.helpers.resolveLocalId(object);
+	if (type !== 'post' || await posts.exists(id)) {
+		throw new Error('[[error:activitypub.invalid-id]]');
+	}
 
-	await posts.upvote(pid, actor);
+	await posts.upvote(id, actor);
 };
 
 inbox.follow = async (req) => {
 	// Sanity checks
-	const localUid = await helpers.resolveLocalUid(req.body.object);
-	if (!localUid) {
-		throw new Error('[[error:invalid-uid]]');
+	const { type, id } = await helpers.resolveLocalId(req.body.object);
+	if (!['category', 'user'].includes(type)) {
+		throw new Error('[[error:activitypub.invalid-id]]');
 	}
 
 	const assertion = await activitypub.actors.assert(req.body.actor);
@@ -73,24 +77,53 @@ inbox.follow = async (req) => {
 		throw new Error('[[error:activitypub.invalid-id]]');
 	}
 
-	const isFollowed = await inbox.isFollowed(req.body.actor, localUid);
-	if (isFollowed) {
-		// No additional parsing required
-		return;
+	if (type === 'user') {
+		const exists = await user.exists(id);
+		if (!exists) {
+			throw new Error('[[error:invalid-uid]]');
+		}
+
+		const isFollowed = await inbox.isFollowed(req.body.actor, id);
+		if (isFollowed) {
+			// No additional parsing required
+			return;
+		}
+
+		const now = Date.now();
+		await db.sortedSetAdd(`followersRemote:${id}`, now, req.body.actor);
+
+		const followerRemoteCount = await db.sortedSetCard(`followersRemote:${id}`);
+		await user.setUserField(id, 'followerRemoteCount', followerRemoteCount);
+
+		await activitypub.send('uid', id, req.body.actor, {
+			type: 'Accept',
+			object: {
+				type: 'Follow',
+				actor: req.body.actor,
+			},
+		});
+	} else if (type === 'category') {
+		const exists = await categories.exists(id);
+		if (!exists) {
+			throw new Error('[[error:invalid-cid]]');
+		}
+
+		const watchState = await categories.getWatchState([id], req.body.actor);
+		if (watchState === categories.watchStates.tracking) {
+			// No additional parsing required
+			return;
+		}
+
+		await user.setCategoryWatchState(req.body.actor, id, categories.watchStates.tracking);
+
+		await activitypub.send('cid', id, req.body.actor, {
+			type: 'Accept',
+			object: {
+				type: 'Follow',
+				actor: req.body.actor,
+			},
+		});
 	}
-
-	const now = Date.now();
-	await db.sortedSetAdd(`followersRemote:${localUid}`, now, req.body.actor);
-	await activitypub.send(localUid, req.body.actor, {
-		type: 'Accept',
-		object: {
-			type: 'Follow',
-			actor: req.body.actor,
-		},
-	});
-
-	const followerRemoteCount = await db.sortedSetCard(`followersRemote:${localUid}`);
-	await user.setUserField(localUid, 'followerRemoteCount', followerRemoteCount);
 };
 
 inbox.isFollowed = async (actorId, uid) => {
@@ -104,8 +137,8 @@ inbox.accept = async (req) => {
 	const { actor, object } = req.body;
 	const { type } = object;
 
-	const uid = await helpers.resolveLocalUid(object.actor);
-	if (!uid) {
+	const { type: localType, id: uid } = await helpers.resolveLocalId(object.actor);
+	if (localType !== 'user' || !uid) {
 		throw new Error('[[error:invalid-uid]]');
 	}
 
@@ -124,6 +157,7 @@ inbox.accept = async (req) => {
 };
 
 inbox.undo = async (req) => {
+	// todo: "actor" in this case should be the one in object, no?
 	const { actor, object } = req.body;
 	const { type } = object;
 
@@ -132,23 +166,45 @@ inbox.undo = async (req) => {
 		throw new Error('[[error:activitypub.invalid-id]]');
 	}
 
+	const { type: localType, id } = await helpers.resolveLocalId(object.object);
+
 	switch (type) {
 		case 'Follow': {
-			const uid = await helpers.resolveLocalUid(object.object);
-			if (!uid) {
-				throw new Error('[[error:invalid-uid]]');
+			switch (localType) {
+				case 'user': {
+					const exists = await user.exists(id);
+					if (!exists) {
+						throw new Error('[[error:invalid-uid]]');
+					}
+
+					await Promise.all([
+						db.sortedSetRemove(`followersRemote:${id}`, actor),
+						db.decrObjectField(`user:${id}`, 'followerRemoteCount'),
+					]);
+					break;
+				}
+
+				case 'category': {
+					const exists = await categories.exists(id);
+					if (!exists) {
+						throw new Error('[[error:invalid-cid]]');
+					}
+
+					await user.setCategoryWatchState(actor, id, categories.watchStates.notwatching);
+					break;
+				}
 			}
 
-			await Promise.all([
-				db.sortedSetRemove(`followersRemote:${uid}`, actor),
-				db.decrObjectField(`user:${uid}`, 'followerRemoteCount'),
-			]);
 			break;
 		}
 
 		case 'Like': {
-			const pid = await helpers.resolveLocalPid(object.object);
-			await posts.unvote(pid, actor);
+			const exists = await posts.exists(id);
+			if (localType !== 'post' || !exists) {
+				throw new Error('[[error:invalid-pid]]');
+			}
+
+			await posts.unvote(id, actor);
 			break;
 		}
 	}
diff --git a/src/activitypub/index.js b/src/activitypub/index.js
index 4957217f72..63ec8eca49 100644
--- a/src/activitypub/index.js
+++ b/src/activitypub/index.js
@@ -37,28 +37,40 @@ ActivityPub.resolveInboxes = async (ids) => {
 	return Array.from(inboxes);
 };
 
-ActivityPub.getPublicKey = async (uid) => {
+ActivityPub.getPublicKey = async (type, id) => {
 	let publicKey;
 
 	try {
-		({ publicKey } = await db.getObject(`uid:${uid}:keys`));
+		({ publicKey } = await db.getObject(`uid:${id}:keys`));
 	} catch (e) {
-		({ publicKey } = await ActivityPub.helpers.generateKeys(uid));
+		({ publicKey } = await ActivityPub.helpers.generateKeys(type, id));
 	}
 
 	return publicKey;
 };
 
-ActivityPub.getPrivateKey = async (uid) => {
+ActivityPub.getPrivateKey = async (type, id) => {
+	// Sanity checking
+	if (!['cid', 'uid'].includes(type) || !utils.isNumber(id) || parseInt(id, 10) < 0) {
+		throw new Error('[[error:invalid-data]]');
+	}
+	id = parseInt(id, 10);
 	let privateKey;
 
 	try {
-		({ privateKey } = await db.getObject(`uid:${uid}:keys`));
+		({ privateKey } = await db.getObject(`${type}:${id}:keys`));
 	} catch (e) {
-		({ privateKey } = await ActivityPub.helpers.generateKeys(uid));
+		({ privateKey } = await ActivityPub.helpers.generateKeys(type, id));
 	}
 
-	return privateKey;
+	let keyId;
+	if (type === 'uid') {
+		keyId = `${nconf.get('url')}${id > 0 ? `/uid/${id}` : '/actor'}#key`;
+	} else {
+		keyId = `${nconf.get('url')}/category/${id}#key`;
+	}
+
+	return { key: privateKey, keyId };
 };
 
 ActivityPub.fetchPublicKey = async (uri) => {
@@ -76,18 +88,10 @@ ActivityPub.fetchPublicKey = async (uri) => {
 	return body.publicKey;
 };
 
-ActivityPub.sign = async (uid, url, payload) => {
-	// Sanity checking
-	if (!utils.isNumber(uid) || parseInt(uid, 10) < 0) {
-		throw new Error('[[error:invalid-uid]]');
-	}
-	uid = parseInt(uid, 10);
-
+ActivityPub.sign = async ({ key, keyId }, url, payload) => {
 	// Returns string for use in 'Signature' header
 	const { host, pathname } = new URL(url);
 	const date = new Date().toUTCString();
-	const key = await ActivityPub.getPrivateKey(uid);
-	const keyId = `${nconf.get('url')}${uid > 0 ? `/uid/${uid}` : '/actor'}#key`;
 	let digest = null;
 
 	let headers = '(request-target) host date';
@@ -156,13 +160,14 @@ ActivityPub.verify = async (req) => {
 	}
 };
 
-ActivityPub.get = async (uid, uri) => {
-	const cacheKey = [uid, uri].join(';');
+ActivityPub.get = async (type, id, uri) => {
+	const cacheKey = [id, uri].join(';');
 	if (requestCache.has(cacheKey)) {
 		return requestCache.get(cacheKey);
 	}
 
-	const headers = uid >= 0 ? await ActivityPub.sign(uid, uri) : {};
+	const keyData = await ActivityPub.getPrivateKey(type, id);
+	const headers = id >= 0 ? await ActivityPub.sign(keyData, uri) : {};
 	winston.verbose(`[activitypub/get] ${uri}`);
 	const { response, body } = await request.get(uri, {
 		headers: {
@@ -184,7 +189,7 @@ ActivityPub.get = async (uid, uri) => {
 	return body;
 };
 
-ActivityPub.send = async (uid, targets, payload) => {
+ActivityPub.send = async (type, id, targets, payload) => {
 	if (!Array.isArray(targets)) {
 		targets = [targets];
 	}
@@ -193,12 +198,14 @@ ActivityPub.send = async (uid, targets, payload) => {
 
 	payload = {
 		'@context': 'https://www.w3.org/ns/activitystreams',
-		actor: `${nconf.get('url')}/uid/${uid}`,
+		actor: `${nconf.get('url')}/uid/${id}`,
 		...payload,
 	};
 
 	await Promise.all(inboxes.map(async (uri) => {
-		const headers = await ActivityPub.sign(uid, uri, payload);
+		const keyData = await ActivityPub.getPrivateKey(type, id);
+		const headers = await ActivityPub.sign(keyData, uri, payload);
+		winston.verbose(`[activitypub/send] ${uri}`);
 		const { response } = await request.post(uri, {
 			headers: {
 				...headers,
diff --git a/src/activitypub/mocks.js b/src/activitypub/mocks.js
index 04c6c2aefc..1e4e017f10 100644
--- a/src/activitypub/mocks.js
+++ b/src/activitypub/mocks.js
@@ -118,7 +118,7 @@ Mocks.actors = {};
 
 Mocks.actors.user = async (uid) => {
 	let { username, userslug, displayname: name, aboutme, picture, 'cover:url': cover } = await user.getUserData(uid);
-	const publicKey = await activitypub.getPublicKey(uid);
+	const publicKey = await activitypub.getPublicKey('uid', uid);
 
 	if (picture) {
 		const imagePath = await user.getLocalAvatarPath(uid);
diff --git a/src/activitypub/notes.js b/src/activitypub/notes.js
index 75735cbde1..f49cb5113a 100644
--- a/src/activitypub/notes.js
+++ b/src/activitypub/notes.js
@@ -12,7 +12,7 @@ const activitypub = module.parent.exports;
 const Notes = module.exports;
 
 Notes.resolveId = async (uid, id) => {
-	({ id } = await activitypub.get(uid, id));
+	({ id } = await activitypub.get('uid', uid, id));
 	return id;
 };
 
@@ -30,7 +30,7 @@ Notes.assert = async (uid, input, options = {}) => {
 			let postData;
 			winston.verbose(`[activitypub/notes.assert] Not found, saving note to database`);
 			if (activitypub.helpers.isUri(item)) {
-				const object = await activitypub.get(uid, item);
+				const object = await activitypub.get('uid', uid, item);
 				postData = await activitypub.mocks.post(object);
 			} else {
 				postData = item;
@@ -60,7 +60,7 @@ Notes.getParentChain = async (uid, input) => {
 				await traverse(uid, postData.toPid);
 			}
 		} else {
-			let object = await activitypub.get(uid, id);
+			let object = await activitypub.get('uid', uid, id);
 			object = await activitypub.mocks.post(object);
 			if (object) {
 				chain.add(object);
diff --git a/src/api/activitypub.js b/src/api/activitypub.js
index 2152a75444..857e0a0184 100644
--- a/src/api/activitypub.js
+++ b/src/api/activitypub.js
@@ -22,7 +22,7 @@ activitypubApi.follow = async (caller, { uid } = {}) => {
 		throw new Error('[[error:activitypub.invalid-id]]');
 	}
 
-	await activitypub.send(caller.uid, [result.actorUri], {
+	await activitypub.send('uid', caller.uid, [result.actorUri], {
 		type: 'Follow',
 		object: result.actorUri,
 	});
@@ -35,7 +35,7 @@ activitypubApi.unfollow = async (caller, { uid }) => {
 		throw new Error('[[error:activitypub.invalid-id]]');
 	}
 
-	await activitypub.send(caller.uid, [result.actorUri], {
+	await activitypub.send('uid', caller.uid, [result.actorUri], {
 		type: 'Undo',
 		object: {
 			type: 'Follow',
@@ -81,7 +81,7 @@ activitypubApi.create.post = async (caller, { pid }) => {
 		object,
 	};
 
-	await activitypub.send(caller.uid, Array.from(targets), payload);
+	await activitypub.send('uid', caller.uid, Array.from(targets), payload);
 };
 
 activitypubApi.update = {};
@@ -92,7 +92,7 @@ activitypubApi.update.profile = async (caller, { uid }) => {
 		db.getSortedSetMembers(`followersRemote:${caller.uid}`),
 	]);
 
-	await activitypub.send(caller.uid, followers, {
+	await activitypub.send('uid', caller.uid, followers, {
 		type: 'Update',
 		to: [activitypub._constants.publicAddress],
 		cc: [],
@@ -111,7 +111,7 @@ activitypubApi.update.note = async (caller, { post }) => {
 		object,
 	};
 
-	await activitypub.send(caller.uid, Array.from(targets), payload);
+	await activitypub.send('uid', caller.uid, Array.from(targets), payload);
 };
 
 activitypubApi.like = {};
@@ -126,7 +126,7 @@ activitypubApi.like.note = async (caller, { pid }) => {
 		return;
 	}
 
-	await activitypub.send(caller.uid, [uid], {
+	await activitypub.send('uid', caller.uid, [uid], {
 		type: 'Like',
 		object: pid,
 	});
@@ -146,7 +146,7 @@ activitypubApi.undo.like = async (caller, { pid }) => {
 		return;
 	}
 
-	await activitypub.send(caller.uid, [uid], {
+	await activitypub.send('uid', caller.uid, [uid], {
 		type: 'Undo',
 		object: {
 			actor: `${nconf.get('url')}/uid/${caller.uid}`,
diff --git a/src/categories/watch.js b/src/categories/watch.js
index f80d0bf15d..4f53ea01e5 100644
--- a/src/categories/watch.js
+++ b/src/categories/watch.js
@@ -2,6 +2,7 @@
 
 const db = require('../database');
 const user = require('../user');
+const activitypub = require('../activitypub');
 
 module.exports = function (Categories) {
 	Categories.watchStates = {
@@ -20,7 +21,7 @@ module.exports = function (Categories) {
 	};
 
 	Categories.getWatchState = async function (cids, uid) {
-		if (!(parseInt(uid, 10) > 0)) {
+		if (!activitypub.helpers.isUri(uid) && !(parseInt(uid, 10) > 0)) {
 			return cids.map(() => Categories.watchStates.notwatching);
 		}
 		if (!Array.isArray(cids) || !cids.length) {
diff --git a/src/controllers/activitypub/actors.js b/src/controllers/activitypub/actors.js
index adf7758157..b14b46c380 100644
--- a/src/controllers/activitypub/actors.js
+++ b/src/controllers/activitypub/actors.js
@@ -10,7 +10,7 @@ const activitypub = require('../../activitypub');
 const Actors = module.exports;
 
 Actors.application = async function (req, res) {
-	const publicKey = await activitypub.getPublicKey(0);
+	const publicKey = await activitypub.getPublicKey('uid', 0);
 	const name = meta.config.title || 'NodeBB';
 
 	res.status(200).json({
diff --git a/src/user/categories.js b/src/user/categories.js
index 1bae181ef5..137cf595e3 100644
--- a/src/user/categories.js
+++ b/src/user/categories.js
@@ -4,11 +4,12 @@ const _ = require('lodash');
 
 const db = require('../database');
 const categories = require('../categories');
+const activitypub = require('../activitypub');
 const plugins = require('../plugins');
 
 module.exports = function (User) {
 	User.setCategoryWatchState = async function (uid, cids, state) {
-		if (!(parseInt(uid, 10) > 0)) {
+		if (!activitypub.helpers.isUri(uid) && !(parseInt(uid, 10) > 0)) {
 			return;
 		}
 		const isStateValid = Object.values(categories.watchStates).includes(parseInt(state, 10));
diff --git a/src/user/settings.js b/src/user/settings.js
index 9d8c92fdc3..27d999b7cf 100644
--- a/src/user/settings.js
+++ b/src/user/settings.js
@@ -5,6 +5,7 @@ const validator = require('validator');
 
 const meta = require('../meta');
 const db = require('../database');
+const activitypub = require('../activitypub');
 const plugins = require('../plugins');
 const notifications = require('../notifications');
 const languages = require('../languages');
@@ -16,6 +17,10 @@ module.exports = function (User) {
 		postsPerPage: 20,
 		topicsPerPage: 20,
 	};
+	const remoteDefaultSettings = Object.freeze({
+		categoryWatchState: 'notwatching',
+	});
+
 	User.getSettings = async function (uid) {
 		if (parseInt(uid, 10) <= 0) {
 			const isSpider = parseInt(uid, 10) === -1;
@@ -90,6 +95,8 @@ module.exports = function (User) {
 	function getSetting(settings, key, defaultValue) {
 		if (settings[key] || settings[key] === 0) {
 			return settings[key];
+		} else if (activitypub.helpers.isUri(settings.uid) && remoteDefaultSettings[key]) {
+			return remoteDefaultSettings[key];
 		} else if (meta.config[key] || meta.config[key] === 0) {
 			return meta.config[key];
 		}
diff --git a/test/activitypub.js b/test/activitypub.js
index a2af8bf50e..d065563cc9 100644
--- a/test/activitypub.js
+++ b/test/activitypub.js
@@ -88,7 +88,7 @@ describe('ActivityPub integration', () => {
 
 		});
 
-		describe('.resolveLocalUid()', () => {
+		describe('.resolveLocalId()', () => {
 			let uid;
 			let slug;
 
@@ -99,29 +99,29 @@ describe('ActivityPub integration', () => {
 
 			it('should throw when an invalid input is passed in', async () => {
 				await assert.rejects(
-					activitypub.helpers.resolveLocalUid('ncl28h3qwhoiclwnevoinw3u'),
+					activitypub.helpers.resolveLocalId('ncl28h3qwhoiclwnevoinw3u'),
 					{ message: '[[error:activitypub.invalid-id]]' }
 				);
 			});
 
 			it('should return null when valid input is passed but does not resolve', async () => {
-				const uid = await activitypub.helpers.resolveLocalUid(`acct:foobar@${nconf.get('url_parsed').host}`);
-				assert.strictEqual(uid, null);
+				const { id } = await activitypub.helpers.resolveLocalId(`acct:foobar@${nconf.get('url_parsed').host}`);
+				assert.strictEqual(id, null);
 			});
 
 			it('should resolve to a local uid when given a webfinger-style string', async () => {
-				const found = await activitypub.helpers.resolveLocalUid(`acct:${slug}@${nconf.get('url_parsed').host}`);
-				assert.strictEqual(found, uid);
+				const { id } = await activitypub.helpers.resolveLocalId(`acct:${slug}@${nconf.get('url_parsed').host}`);
+				assert.strictEqual(id, uid);
 			});
 
 			it('should resolve even without the "acct:" prefix', async () => {
-				const found = await activitypub.helpers.resolveLocalUid(`${slug}@${nconf.get('url_parsed').host}`);
-				assert.strictEqual(found, uid);
+				const { id } = await activitypub.helpers.resolveLocalId(`${slug}@${nconf.get('url_parsed').host}`);
+				assert.strictEqual(id, uid);
 			});
 
 			it('should resolve when passed a full URL', async () => {
-				const found = await activitypub.helpers.resolveLocalUid(`${nconf.get('url')}/user/${slug}`);
-				assert.strictEqual(found, uid);
+				const { id } = await activitypub.helpers.resolveLocalId(`${nconf.get('url')}/user/${slug}`);
+				assert.strictEqual(id, uid);
 			});
 		});
 	});
@@ -274,7 +274,8 @@ describe('ActivityPub integration', () => {
 
 			it('should create a key-pair for a user if the user does not have one already', async () => {
 				const endpoint = `${nconf.get('url')}/uid/${uid}/inbox`;
-				await activitypub.sign(uid, endpoint);
+				const keyData = await activitypub.getPrivateKey('uid', uid);
+				await activitypub.sign(keyData, endpoint);
 				const { publicKey, privateKey } = await db.getObject(`uid:${uid}:keys`);
 
 				assert(publicKey);
@@ -283,7 +284,8 @@ describe('ActivityPub integration', () => {
 
 			it('should return an object with date, a null digest, and signature, if no payload is passed in', async () => {
 				const endpoint = `${nconf.get('url')}/uid/${uid}/inbox`;
-				const { date, digest, signature } = await activitypub.sign(uid, endpoint);
+				const keyData = await activitypub.getPrivateKey('uid', uid);
+				const { date, digest, signature } = await activitypub.sign(keyData, endpoint);
 				const dateObj = new Date(date);
 
 				assert(signature);
@@ -294,7 +296,8 @@ describe('ActivityPub integration', () => {
 			it('should also return a digest hash if payload is passed in', async () => {
 				const endpoint = `${nconf.get('url')}/uid/${uid}/inbox`;
 				const payload = { foo: 'bar' };
-				const { digest } = await activitypub.sign(uid, endpoint, payload);
+				const keyData = await activitypub.getPrivateKey('uid', uid);
+				const { digest } = await activitypub.sign(keyData, endpoint, payload);
 				const hash = createHash('sha256');
 				hash.update(JSON.stringify(payload));
 				const checksum = hash.digest('base64');
@@ -305,7 +308,8 @@ describe('ActivityPub integration', () => {
 
 			it('should create a key for NodeBB itself if a uid of 0 is passed in', async () => {
 				const endpoint = `${nconf.get('url')}/uid/${uid}/inbox`;
-				await activitypub.sign(0, endpoint);
+				const keyData = await activitypub.getPrivateKey('uid', 0);
+				await activitypub.sign(keyData, endpoint);
 				const { publicKey, privateKey } = await db.getObject(`uid:0:keys`);
 
 				assert(publicKey);
@@ -314,7 +318,8 @@ describe('ActivityPub integration', () => {
 
 			it('should return headers with an appropriate key id uri', async () => {
 				const endpoint = `${nconf.get('url')}/uid/${uid}/inbox`;
-				const { signature } = await activitypub.sign(uid, endpoint);
+				const keyData = await activitypub.getPrivateKey('uid', uid);
+				const { signature } = await activitypub.sign(keyData, endpoint);
 				const [keyId] = signature.split(',');
 
 				assert(signature);
@@ -323,7 +328,8 @@ describe('ActivityPub integration', () => {
 
 			it('should return the instance key id when uid is 0', async () => {
 				const endpoint = `${nconf.get('url')}/uid/${uid}/inbox`;
-				const { signature } = await activitypub.sign(0, endpoint);
+				const keyData = await activitypub.getPrivateKey('uid', 0);
+				const { signature } = await activitypub.sign(keyData, endpoint);
 				const [keyId] = signature.split(',');
 
 				assert(signature);
@@ -355,7 +361,8 @@ describe('ActivityPub integration', () => {
 			it('should return true when the proper signature and relevant headers are passed in', async () => {
 				const endpoint = `${nconf.get('url')}/user/${username}/inbox`;
 				const path = `/user/${username}/inbox`;
-				const signature = await activitypub.sign(uid, endpoint);
+				const keyData = await activitypub.getPrivateKey('uid', uid);
+				const signature = await activitypub.sign(keyData, endpoint);
 				const { host } = nconf.get('url_parsed');
 				const req = {
 					...mockReqBase,
@@ -372,7 +379,8 @@ describe('ActivityPub integration', () => {
 			it('should return true when a digest is also passed in', async () => {
 				const endpoint = `${nconf.get('url')}/user/${username}/inbox`;
 				const path = `/user/${username}/inbox`;
-				const signature = await activitypub.sign(uid, endpoint, { foo: 'bar' });
+				const keyData = await activitypub.getPrivateKey('uid', uid);
+				const signature = await activitypub.sign(keyData, endpoint, { foo: 'bar' });
 				const { host } = nconf.get('url_parsed');
 				const req = {
 					...mockReqBase,
@@ -412,7 +420,7 @@ describe('ActivityPub integration', () => {
 					const post = (await posts.getPostSummaryByPids([postData.pid], uid, { stripTags: false })).pop();
 					note = await activitypub.mocks.note(post);
 
-					await activitypub.send(uid, [`${nconf.get('url')}/uid/${uid}`], {
+					await activitypub.send('uid', uid, [`${nconf.get('url')}/uid/${uid}`], {
 						type: 'Create',
 						object: note,
 					});