diff --git a/source/api/actions/member_register.ts b/source/api/actions/member_register.ts
index a03b1d8..afe3055 100644
--- a/source/api/actions/member_register.ts
+++ b/source/api/actions/member_register.ts
@@ -15,7 +15,12 @@ namespace _espe.api
 				email_redirect_to_private_address : boolean;
 				password : (null | string);
 			},
-			null
+			Array<
+				{
+					incident : string;
+					details : Record<string, any>;
+				}
+			>
 		>(
 			rest_subject,
 			lib_plankton.http.enum_method.post,
@@ -65,7 +70,7 @@ namespace _espe.api
 					stuff => parseInt(stuff.path_parameters["id"]),
 					stuff => stuff.query_parameters["key"]
 				),
-				"execution": async ({"path_parameters": path_parameters, "input": input}) => {
+				"execution": ({"path_parameters": path_parameters, "input": input}) => {
 					const member_id : _espe.type.member_id = parseInt(path_parameters["id"]);
 					return (
 						_espe.service.member.register(
@@ -78,15 +83,13 @@ namespace _espe.api
 							}
 						)
 						.then(
-							() => Promise.resolve({
-								"status_code": 200,
-								"data": null,
-							})
-						)
-						.catch(
-							() => Promise.resolve({
-								"status_code": 409,
-								"data": /*"bereits registriert"*/null,
+							flaws => Promise.resolve({
+								"status_code": (
+									(flaws.length <= 0)
+									? 200
+									: 409
+								),
+								"data": flaws
 							})
 						)
 					);
diff --git a/source/services/member.ts b/source/services/member.ts
index 5cf0570..605de49 100644
--- a/source/services/member.ts
+++ b/source/services/member.ts
@@ -29,6 +29,78 @@ namespace _espe.service.member
 	}
 	
 	
+	/**
+	 * @todo test
+	 */
+	function validate_password(
+		password : string
+	) : Array<{incident : string; details : Record<string, any>}>
+	{
+		let flaws : Array<{incident : string; details : Record<string, any>}> = [];
+		
+		const conf = {
+			"minimum_length": 8,
+			"maximum_length": 240,
+			// "pattern": 
+			"must_contain_letter": true,
+			"must_contain_number": true,
+			"must_contain_special_character": true,
+		};
+		
+		if (password.length < conf.minimum_length) {
+			flaws.push(
+				{
+					"incident": "too_short",
+					"details": {
+						"minimum_length": conf.minimum_length,
+						"actual_length": password.length,
+					}
+				}
+			);
+		}
+		if (password.length > conf.maximum_length) {
+			flaws.push(
+				{
+					"incident": "too_long",
+					"details": {
+						"maximum_length": conf.maximum_length,
+						"actual_length": password.length,
+					}
+				}
+			);
+		}
+		if (conf.must_contain_letter && (! (new RegExp("[a-zA-Z]")).test(password))) {
+			flaws.push(
+				{
+					"incident": "lacks_letter",
+					"details": {
+					}
+				}
+			);
+		}
+		if (conf.must_contain_number && (! (new RegExp("[0-9]")).test(password))) {
+			flaws.push(
+				{
+					"incident": "lacks_number",
+					"details": {
+					}
+				}
+			);
+		}
+		if (conf.must_contain_special_character && (! (new RegExp("[!?-_.,;/\~%&$'()\\[\\]{}^'#|+*<>=\"`:@]")).test(password))) {
+			flaws.push(
+				{
+					"incident": "lacks_special_character",
+					"details": {
+					}
+				}
+			);
+		}
+		
+		return flaws;
+	}
+	
+	
 	/**
 	 */
 	export function name_login(
@@ -38,7 +110,17 @@ namespace _espe.service.member
 		return lib_plankton.string.coin(
 			"{{object}}{{extension}}",
 			{
-				"object": object.name_real_value.toLowerCase().replace(new RegExp(" ", "g"), "."),
+				"object": lib_plankton.call.convey(
+					object.name_real_value,
+					[
+						x => x.toLowerCase(),
+						x => x.replace(new RegExp(" ", "g"), "."),
+						x => x.replace(new RegExp("ä", "g"), "ae"),
+						x => x.replace(new RegExp("ö", "g"), "oe"),
+						x => x.replace(new RegExp("ü", "g"), "ue"),
+						x => x.replace(new RegExp("ß", "g"), "ss"),
+					]
+				),
 				"extension": (
 					(object.name_real_index <= 1)
 					? ""
@@ -267,7 +349,7 @@ namespace _espe.service.member
 		options : {
 			notify_admins ?: boolean;
 		} = {}
-	) : Promise<void>
+	) : Promise<Array<{incident : string; details : Record<string, any>;}>>
 	{
 		options = Object.assign(
 			{
@@ -275,31 +357,59 @@ namespace _espe.service.member
 			},
 			options
 		);
+		
 		const member_object : _espe.type.member_object = await get(member_id);
+		let flaws : Array<{incident : string; details : Record<string, any>;}> = [];
+		const password_set : boolean = (
+			(data.password !== null)
+			&&
+			(data.password !== "")
+		);
 		if (member_object.registered) {
-			return Promise.reject(new Error("already registered"));
+			flaws.push({"incident": "already_registered", "details": {}});
+		}
+		else {
+			if (password_set) {
+				flaws = flaws.concat(
+					validate_password(data.password)
+					.map(flaw => ({"incident": ("password_" + flaw.incident), "details": flaw.details}))
+				);
+			}
+			else {
+				// do nothing
+			}
+		}
+		
+		if (flaws.length > 0) {
+			// do nothing
 		}
 		else {
 			member_object.email_use_veiled_address = data.email_use_veiled_address
 			member_object.email_use_nominal_address = data.email_use_nominal_address
 			member_object.email_redirect_to_private_address = data.email_redirect_to_private_address;
-			member_object.password_image = await _espe.helpers.bcrypt_compute(data.password);
+			member_object.password_image = (
+				password_set
+				? await _espe.helpers.bcrypt_compute(data.password)
+				: null
+			);
 			member_object.registered = true;
 			await _espe.repository.member.update(member_id, member_object);
+			
+			notify_change();
+			
+			if (! options.notify_admins) {
+				// do nothing
+			}
+			else {
+				await _espe.helpers.email_send(
+					_espe.conf.get().admins.map(admin => admin.email_address).filter(x => (x !== null)),
+					"Eingegangene Registrierung",
+					("Member-ID: " + member_id.toFixed(0))
+				);
+			}
 		}
 		
-		notify_change();
-		
-		if (! options.notify_admins) {
-			// do nothing
-		}
-		else {
-			await _espe.helpers.email_send(
-				_espe.conf.get().admins.map(admin => admin.email_address).filter(x => (x !== null)),
-				"Eingegangene Registrierung",
-				("Member-ID: " + member_id.toFixed(0))
-			);
-		}
+		return Promise.resolve(flaws);
 	}