diff --git a/protocol-spec/account-login-by-username.md b/protocol-spec/account-login-by-username.md
new file mode 100644
index 0000000..1fd024a
--- /dev/null
+++ b/protocol-spec/account-login-by-username.md
@@ -0,0 +1,87 @@
+# Account login by username
+## Introduction
+This extension is intended for logging into user account on a server by username
+
+## Message type identifiers
+- `profile:login`  
+
+## Error codes
+- 0: limit exceed
+- 1: user ID/password isn't valid
+
+## Use cases
+*Request*:
+```json
+{
+    "id": "abcd",
+    "type": "profile:login",
+    "to": "cadmium.org",
+    "payload": {
+        "username": "juliet",
+        "password": "romeo1"
+    }
+}
+```
+
+*Response*:
+```json
+{
+    "id": "abcd",
+    "type": "profile:login",
+    "from": "cadmium.org",
+    "ok": true,
+    "payload": {
+        "authToken": "3b5135a5-aff5-4396-a629-a254f383e82f",
+        "deviceID": "ABCDEFG"
+    }
+}
+```
+
+*<b>Error</b> response*:
+```json
+{
+    "id": "abcd",
+    "type": "profile:login",
+    "from": "cadmium.org",
+    "ok": false,
+    "payload": {
+        "errCode": 1,
+        "errText": "Username/password isn't valid"
+    }
+}
+```
+
+## Business Rules
+None.
+
+## JSON Schema
+**Payload**
+
+- Request:
+```typescript
+interface LoginRequestPayload {
+    /**
+     * The username of account which user wants to login
+     */
+    username: string,
+    
+    /**
+     * Password of new account
+     */
+    password: string
+}
+```
+- Response:
+```typescript
+interface LoginResponsePayload {
+    /**
+     * Authentication token which required for various user actions (UUID)
+     */
+    authToken: string,
+    
+    /**
+     * Identifier of new user device (created by this login action)
+     */
+    deviceID: string
+}
+```
\ No newline at end of file
diff --git a/protocol-spec/core.md b/protocol-spec/core.md
index 334cda3..b830602 100644
--- a/protocol-spec/core.md
+++ b/protocol-spec/core.md
@@ -4,10 +4,7 @@
   - [Transport](#transport)
   - [Entity ID](#entity-id)
   - [BaseMessage](#basemessage)
-  - [Errors](#errors)
   - [User devices](#user-devices)
-  - [Account registration/login](#account-registrationlogin)
-    - [Login into account (by username)](#login-into-account-by-username)
 
 ## Transport
 For starting we simply use JSON + Websockets.
@@ -69,144 +66,6 @@ interface BaseMessage {
 }
 ```
 
-## Errors
-Mechanism of error processing included into protocol.
-Adds into type name `:error` postfix.
-
-**Payload**:
-```typescript
-interface ErrorPayload {
-    /**
-     * Error code (defined in extensions, may be same per extensions)
-     */
-    errCode: number,
-
-    /**
-     * Explanation of error in human-readable view
-     */
-    errText: string,
-
-    /**
-     * Advanced error information (fields defined in extensions)
-     */
-    errPayload: Map<K,V>
-}
-```
-
-**Usecase**:  
-
-*Request*:
-```json
-{
-    "id": "abcd",
-    "type": "incorrectMessageType",
-    "from": "@juliet@cadmium.im",
-    "to": "cadmium.im",
-    "payload": {
-        "test": "test"
-    }
-}
-```
-
-*Response*:
-```json
-{
-    "id": "abcd",
-    "type": "incorrectMessageType:error",
-    "from": "cadmium.im",
-    "to": "@juliet@cadmium.im",
-    "payload": {
-        "errCode": 0,
-        "errText": "Incorrect type of message (type isn't implemented in the server)",
-        "errPayload": {}
-    }
-}
-```
-
 ## User devices
 `todo`
 
-## Account registration/login
-
-### Login into account (by username)
-**Description**: Login into user account on a server by username
-**Type**: `profile:login`  
-**Payload**:
-- Request:
-```typescript
-interface LoginRequestPayload {
-    /**
-     * The username of account which user wants to login
-     */
-    username: string,
-    
-    /**
-     * Password of new account
-     */
-    password: string
-}
-```
-- Response:
-```typescript
-interface LoginResponsePayload {
-    /**
-     * Authentication token which required for various user actions (UUID)
-     */
-    authToken: string,
-    
-    /**
-     * Identifier of new user device (created by this login action)
-     */
-    deviceID: string
-}
-```
-
-**Errors**:  
-- 0: limit exceed
-- 1: user ID/password isn't valid
-
-**Usecase**:
-
-*Request*:
-```json
-{
-    "id": "abcd",
-    "type": "profile:login",
-    "to": "cadmium.org",
-    "payload": {
-        "username": "juliet",
-        "password": "romeo1"
-    }
-}
-```
-
-*Response*:
-```json
-{
-    "id": "abcd",
-    "type": "profile:login",
-    "from": "cadmium.org",
-    "ok": true,
-    "payload": {
-        "authToken": "3b5135a5-aff5-4396-a629-a254f383e82f",
-        "deviceID": "ABCDEFG"
-    }
-}
-```
-
-*<b>Error</b> response*:
-```json
-{
-    "id": "abcd",
-    "type": "profile:login",
-    "from": "cadmium.org",
-    "ok": false,
-    "payload": {
-        "errCode": 1,
-        "errText": "Username/password isn't valid"
-    }
-}
-```
-
-**Special business rules**: none.
-
diff --git a/protocol-spec/protocol-errors.md b/protocol-spec/protocol-errors.md
new file mode 100644
index 0000000..a9c52c3
--- /dev/null
+++ b/protocol-spec/protocol-errors.md
@@ -0,0 +1,58 @@
+# Protocol Errors
+## Introduction
+Mechanism of error processing included into protocol.  
+Adds into any type ID `:error` postfix.
+
+## Message type identifiers
+- `*:error`
+
+## Use cases
+*Request*:
+```json
+{
+    "id": "abcd",
+    "type": "incorrectMessageType",
+    "from": "@juliet@cadmium.im",
+    "to": "cadmium.im",
+    "payload": {
+        "test": "test"
+    }
+}
+```
+
+*Response*:
+```json
+{
+    "id": "abcd",
+    "type": "incorrectMessageType:error",
+    "from": "cadmium.im",
+    "to": "@juliet@cadmium.im",
+    "payload": {
+        "errCode": 0,
+        "errText": "Incorrect type of message (type isn't implemented in the server)",
+        "errPayload": {}
+    }
+}
+```
+
+## JSON Schema
+**Payload**
+
+```typescript
+interface ErrorPayload {
+    /**
+     * Error code (defined in extensions, may be same per extensions)
+     */
+    errCode: number,
+
+    /**
+     * Explanation of error in human-readable view
+     */
+    errText: string,
+
+    /**
+     * Advanced error information (fields defined in extensions)
+     */
+    errPayload: Map<K,V>
+}
+```
\ No newline at end of file