diff --git a/lib/crypto/Crypto.js b/lib/crypto/Crypto.js
index 282183d..7a6db0e 100644
--- a/lib/crypto/Crypto.js
+++ b/lib/crypto/Crypto.js
@@ -2,15 +2,14 @@
 
 const crypto = require('crypto');
 
-const BN = require('bn.js');
-
+const BigNumber = require('../BigNumber.js');
 const mgf1 = require('./MGF1');
 
 const modPow = (base, power, mod) => {
-	let result = new BN(1);
+	let result = new BigNumber(1);
 
 	while (power > 0) {
-		result = power.and(new BN(1)) == 1 ? (result.mul(base)).mod(mod) : result; // eslint-disable-line
+		result = power.and(new BigNumber(1)) == 1 ? (result.mul(base)).mod(mod) : result; // eslint-disable-line
 		base = (base.mul(base)).mod(mod);
 		power = power.shrn(1);
 	}
@@ -28,10 +27,13 @@ const emsaPSS = (msg, salt) => {
 	const dbMask = mgf1.generate(mTickHash, db.length);
 	const maskedDb = mgf1.xor(db, dbMask);
 
-	let maskedDbMsb = mgf1.rjust(new BN(maskedDb.slice(0, 1), 2).toString(2), 8, '0');
+	let maskedDbMsb = mgf1.rjust(BigNumber.fromBuffer(maskedDb.slice(0, 1)).toString(2), 8, '0');
+
 
 	maskedDbMsb = `0${maskedDbMsb.substr(1)}`;
-	maskedDb[0] = (new BN(maskedDbMsb, 2).toBuffer())[0]; // eslint-disable-line
+	// console.log((new BN(maskedDbMsb, 2).toBuffer())[0], new BigNumber(maskedDbMsb, 2).toBuffer()[0]);
+	// maskedDb[0] = (new BN(maskedDbMsb, 2).toBuffer())[0]; // eslint-disable-line
+	maskedDb[0] = new BigNumber(maskedDbMsb, 2).toBuffer()[0]; // eslint-disable-line
 
 	return Buffer.concat([maskedDb, mTickHash, Buffer.from('BC', 'hex')]);
 };
@@ -65,9 +67,10 @@ module.exports = class Crypto {
 	}
 
 	static sign(key, msg, salt = crypto.randomBytes(32)) {
-		const base = new BN(emsaPSS(msg, salt));
-		const power = new BN(key.d());
-		const mod = new BN(key.n());
+		// console.log(key.d());
+		const base = new BigNumber(emsaPSS(msg, salt));
+		const power = new BigNumber(key.d());
+		const mod = new BigNumber(key.n());
 
 		return (modPow(base, power, mod)).toBuffer().toString('base64');
 	}