diff --git a/keyserver/src/database/migration-config.js b/keyserver/src/database/migration-config.js
--- a/keyserver/src/database/migration-config.js
+++ b/keyserver/src/database/migration-config.js
@@ -47,19 +47,6 @@
       `);
     },
   ],
-  [
-    6,
-    async () => {
-      await dbQuery(SQL`
-        ALTER TABLE users
-          DROP COLUMN public_key,
-          MODIFY hash char(60) COLLATE utf8mb4_bin DEFAULT NULL;
-  
-        ALTER TABLE sessions 
-          DROP COLUMN public_key;
-      `);
-    },
-  ],
 ]);
 const newDatabaseVersion: number = Math.max(...migrations.keys());
 
diff --git a/keyserver/src/database/setup-db.js b/keyserver/src/database/setup-db.js
--- a/keyserver/src/database/setup-db.js
+++ b/keyserver/src/database/setup-db.js
@@ -136,7 +136,8 @@
         query json NOT NULL,
         creation_time bigint(20) NOT NULL,
         last_update bigint(20) NOT NULL,
-        last_validated bigint(20) NOT NULL
+        last_validated bigint(20) NOT NULL,
+        public_key char(116) DEFAULT NULL
       ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
 
       CREATE TABLE threads (
@@ -183,9 +184,10 @@
       CREATE TABLE users (
         id bigint(20) NOT NULL,
         username varchar(${usernameMaxLength}) COLLATE utf8mb4_bin NOT NULL,
-        hash char(60) COLLATE utf8mb4_bin DEFAULT NULL,
+        hash char(60) COLLATE utf8mb4_bin NOT NULL,
         avatar varchar(191) COLLATE utf8mb4_bin DEFAULT NULL,
-        creation_time bigint(20) NOT NULL
+        creation_time bigint(20) NOT NULL,
+        public_key char(116) DEFAULT NULL
       ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin;
 
       CREATE TABLE relationships_undirected (
@@ -287,7 +289,8 @@
 
       ALTER TABLE sessions
         ADD PRIMARY KEY (id),
-        ADD KEY user (user);
+        ADD KEY user (user),
+        ADD UNIQUE INDEX public_key (public_key);
 
       ALTER TABLE threads
         ADD PRIMARY KEY (id),
@@ -309,7 +312,8 @@
 
       ALTER TABLE users
         ADD PRIMARY KEY (id),
-        ADD UNIQUE KEY username (username);
+        ADD UNIQUE KEY username (username),
+        ADD UNIQUE INDEX public_key (public_key);
 
       ALTER TABLE relationships_undirected
         ADD UNIQUE KEY user1_user2 (user1,user2),