diff --git a/index.js b/index.js
index f90a594..3b26213 100644
--- a/index.js
+++ b/index.js
@@ -3,9 +3,11 @@
 const Client = require('./lib/Client');
 const Orders = require('./lib/predefinedOrders');
 const fsKeysStorage = require('./lib/storages/fsKeysStorage');
+const BankLetter = require('./lib/BankLetter');
 
 module.exports = {
 	Client,
 	Orders,
+	BankLetter,
 	fsKeysStorage,
 };
diff --git a/lib/BankLetter.js b/lib/BankLetter.js
index a31e404..d32c132 100644
--- a/lib/BankLetter.js
+++ b/lib/BankLetter.js
@@ -1,15 +1,19 @@
 'use strict';
 
+const fs = require('fs');
+
 const moment = require('moment');
 const handlebars = require('handlebars');
-const BN = require('bn.js');
+const Crypto = require('./crypto/Crypto');
+// const BN = require('bn.js');
 
 const registerHelpers = () => {
 	handlebars.registerHelper('today', () => moment().format('DD.MM.YYYY'));
 
 	handlebars.registerHelper('now', () => moment().format('HH:mm:ss'));
 
-	handlebars.registerHelper('keyExponentBits', k => Buffer.byteLength(new BN(k.key.keyPair.e).toBuffer()) * 8);
+	handlebars.registerHelper('keyExponentBits', k => Buffer.byteLength(k.e()) * 8);
+	// handlebars.registerHelper('keyExponentBits', k => Buffer.byteLength(new BN(k.key.keyPair.e).toBuffer()) * 8);
 
 	handlebars.registerHelper('keyModulusBits', k => k.key.getKeySize());
 	// return Buffer.byteLength(new BN(k.key.keyPair.e).toBuffer()) * 8;
@@ -19,7 +23,8 @@ const registerHelpers = () => {
 	handlebars.registerHelper('keyModulus', k => k.n('hex').toUpperCase().match(/.{1,2}/g).join(' '));
 
 	handlebars.registerHelper('sha256', (k) => {
-		const digest = Buffer.from(k.publicDigest(), 'base64').toString('HEX');
+		const digest = Buffer.from(Crypto.digestPublicKey(k), 'base64').toString('HEX');
+		// const digest = Buffer.from(k.publicDigest(), 'base64').toString('HEX');
 
 		return digest.toUpperCase().match(/.{1,2}/g).join(' ');
 	});
@@ -36,20 +41,33 @@ module.exports = class BankLetter {
 	}
 
 
-	generate() {
+	async generate() {
 		registerHelpers();
 
 		const templ = handlebars.compile(this.template);
+		const keys = await this.client.keys();
 
 		const data = {
 			bankName: this.bankName,
 			userId: this.client.userId,
 			partnerId: this.client.partnerId,
-			A006: this.client.a(),
-			X002: this.client.x(),
-			E002: this.client.e(),
+			A006: keys.a(),
+			X002: keys.x(),
+			E002: keys.e(),
 		};
 
 		return templ(data);
 	}
+
+	async serialize(path) {
+		const letter = await this.generate();
+
+		try {
+			fs.writeFileSync(path, letter);
+			console.log("Data written to file");
+		} catch (error) {
+			console.log(error);
+			throw error;
+		}
+	}
 };