diff --git a/lib/Client.js b/lib/Client.js
index 1ed7c92..78963ca 100644
--- a/lib/Client.js
+++ b/lib/Client.js
@@ -51,14 +51,15 @@ module.exports = class Client {
 		this.keyEncryptor = defaultKeyEncryptor({ passphrase });
 	}
 
-	send(order) {
+	async send(order) {
 		const isInObject = ('operation' in order);
 
 		if (!isInObject) throw new Error('Operation for the order needed');
 
 		if (order.operation.toUpperCase() === constants.orderOperations.ini) return this.initialization(order);
 
-		if (this.keys() === null) throw new Error('No keys provided. Can not send the order or any other order for that matter.');
+		const keys = await this.keys();
+		if (keys === null) throw new Error('No keys provided. Can not send the order or any other order for that matter.');
 
 		if (order.operation.toUpperCase() === constants.orderOperations.upload) return this.upload(order);
 		if (order.operation.toUpperCase() === constants.orderOperations.download) return this.download(order);
@@ -67,7 +68,8 @@ module.exports = class Client {
 	}
 
 	async initialization(order) {
-		if (this.keys() === null) this._generateKeys();
+		const keys = await this.keys();
+		if (keys === null) this._generateKeys();
 
 		const res = await this.ebicsRequest(order);
 		const xml = res.orderData();
@@ -110,20 +112,22 @@ module.exports = class Client {
 	}
 
 	ebicsRequest(order) {
-		return new Promise((resolve, reject) => {
+		return new Promise(async (resolve, reject) => {
 			const { version } = order;
-			const keys = this.keys();
+			const keys = await this.keys();
 
 			$request.post({
 				url: this.url,
-				body: signer.version(version).sign(serializer.use(order, this).toXML(), keys.x()),
+				body: signer.version(version).sign((await serializer.use(order, this)).toXML(), keys.x()),
 				headers: { 'content-type': 'text/xml;charset=UTF-8' },
 			}, (err, res, data) => (err ? reject(err) : resolve(response.version(version)(data, keys))));
 		});
 	}
 
-	keys() {
-		return this._readKeys();
+	async keys() {
+		const keysString = await this._readKeys();
+
+		return keysString ? new Keys(JSON.parse(this.keyEncryptor.decrypt(keysString))) : null;
 	}
 
 	_generateKeys() {
@@ -132,20 +136,28 @@ module.exports = class Client {
 		this._writeKeys(keysObject);
 	}
 
-	setBankKeys(bankKeys) {
-		const keysObject = this.keys();
+	async setBankKeys(bankKeys) {
+		const keysObject = await this.keys();
 
 		keysObject.setBankKeys(bankKeys);
-		this._writeKeys(keysObject);
+		await this._writeKeys(keysObject);
 	}
 
-	_readKeys() {
-		const keysString = this.keyStorage.read();
+	async _readKeys() {
+		try {
+			const keys = await this.keyStorage.read();
 
-		return keysString ? new Keys(JSON.parse(this.keyEncryptor.decrypt(keysString))) : null;
+			return keys;
+		} catch (err) {
+			return null;
+		}
 	}
 
-	_writeKeys(keysObject) {
-		this.keyStorage.write(this.keyEncryptor.encrypt(stringifyKeys(keysObject.keys)));
+	async _writeKeys(keysObject) {
+		try {
+			await this.keyStorage.write(this.keyEncryptor.encrypt(stringifyKeys(keysObject.keys)));
+		} catch (err) {
+			throw err;
+		}
 	}
 };
diff --git a/lib/orders/H004/serializers/download.js b/lib/orders/H004/serializers/download.js
index 4788ee0..4ae2b99 100644
--- a/lib/orders/H004/serializers/download.js
+++ b/lib/orders/H004/serializers/download.js
@@ -7,8 +7,8 @@ const Crypto = require('../../../crypto/Crypto');
 const genericSerializer = require('./generic');
 
 module.exports = {
-	use(order, client) {
-		const keys = client.keys();
+	async use(order, client) {
+		const keys = await client.keys();
 		const ebicsAccount = {
 			partnerId: client.partnerId,
 			userId: client.userId,
diff --git a/lib/orders/H004/serializers/ini.js b/lib/orders/H004/serializers/ini.js
index 2c1f773..195df23 100644
--- a/lib/orders/H004/serializers/ini.js
+++ b/lib/orders/H004/serializers/ini.js
@@ -118,8 +118,8 @@ const process = {
 };
 
 module.exports = {
-	use(order, client) {
-		const keys = client.keys();
+	async use(order, client) {
+		const keys = await client.keys();
 		const { orderDetails, transactionId } = order;
 		const { xmlOptions, xmlSchema, productString } = genericSerializer(client.host, transactionId);
 		const orderType = orderDetails.OrderType.toUpperCase();
diff --git a/lib/orders/H004/serializers/upload.js b/lib/orders/H004/serializers/upload.js
index 84acdd1..1971088 100644
--- a/lib/orders/H004/serializers/upload.js
+++ b/lib/orders/H004/serializers/upload.js
@@ -47,19 +47,17 @@ const encryptedOrderData = (document, transactionKey) => {
 };
 
 module.exports = {
-	use(order, client) {
-		const keys = client.keys();
+	async use(order, client) {
+		const keys = await client.keys();
 		const ebicsAccount = {
 			partnerId: client.partnerId,
 			userId: client.userId,
 			hostId: client.hostId,
 		};
-		const {
-			transactionId, document,
-		} = order;
+		const { transactionId, document } = order;
 		const {
 			rootName, xmlOptions, xmlSchema, transfer,
-		} = downloadSerializer.use(order, client);
+		} = await downloadSerializer.use(order, client);
 
 		this.rootName = rootName;
 		this.xmlOptions = xmlOptions;
diff --git a/lib/storages/fsKeysStorage.js b/lib/storages/fsKeysStorage.js
index 297f8e6..a54835a 100644
--- a/lib/storages/fsKeysStorage.js
+++ b/lib/storages/fsKeysStorage.js
@@ -6,14 +6,24 @@ module.exports = (pathToFile) => {
 	const path = pathToFile;
 
 	return {
-		read() {
-			if (!fs.existsSync(path))
-				return null;
-			return fs.readFileSync(path, { encoding: 'utf8' });
+		write(data) {
+			return new Promise((resolve, reject) => {
+				fs.writeFile(path, data, { encoding: 'utf8' }, (error) => {
+					if (error) throw error;
+
+					return resolve();
+				});
+			});
 		},
 
-		write(data) {
-			fs.writeFileSync(path, data, { encoding: 'utf8' });
+		read() {
+			return new Promise((resolve, reject) => {
+				fs.readFile(path, { encoding: 'utf8' }, (error, data) => {
+					if (error) reject(error);
+
+					return resolve(data);
+				});
+			});
 		},
 	};
 };