diff --git a/composer.json b/composer.json
index 61d30dc2..c76d7758 100644
--- a/composer.json
+++ b/composer.json
@@ -13,7 +13,7 @@
         "guzzlehttp/guzzle": "^6.3|^7.0",
         "PHP": "^7.2|^8.0",
         "kornrunner/keccak": "~1.0",
-        "phpseclib/phpseclib": "~2.0.30",
+        "phpseclib/phpseclib": "^3.0.36",
         "ext-mbstring": "*",
         "react/http": "^1.6.0",
         "react/async": "^4.0.0|^3.1.0",
diff --git a/src/Utils.php b/src/Utils.php
index f0fdd848..09470fb5 100644
--- a/src/Utils.php
+++ b/src/Utils.php
@@ -2,9 +2,9 @@
 
 /**
  * This file is part of web3.php package.
- * 
+ *
  * (c) Kuan-Cheng,Lai <alk03073135@gmail.com>
- * 
+ *
  * @author Peter Lai <alk03073135@gmail.com>
  * @license MIT
  */
@@ -15,13 +15,13 @@
 use InvalidArgumentException;
 use stdClass;
 use kornrunner\Keccak;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 
 class Utils
 {
     /**
      * SHA3_NULL_HASH
-     * 
+     *
      * @const string
      */
     const SHA3_NULL_HASH = 'c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470';
@@ -29,7 +29,7 @@ class Utils
     /**
      * UNITS
      * from ethjs-unit
-     * 
+     *
      * @const array
      */
     const UNITS = [
@@ -65,7 +65,7 @@ class Utils
     /**
      * NEGATIVE1
      * Cannot work, see: http://php.net/manual/en/language.constants.syntax.php
-     * 
+     *
      * @const
      */
     // const NEGATIVE1 = new BigNumber(-1);
@@ -80,7 +80,7 @@ class Utils
     /**
      * toHex
      * Encoding string or integer or numeric string(is not zero prefixed) or big number to hex.
-     * 
+     *
      * @param string|int|BigNumber $value
      * @param bool $isPrefix
      * @return string
@@ -108,7 +108,7 @@ public static function toHex($value, $isPrefix=false)
 
     /**
      * hexToBin
-     * 
+     *
      * @param string
      * @return string
      */
@@ -130,7 +130,7 @@ public static function hexToBin($value)
 
     /**
      * isZeroPrefixed
-     * 
+     *
      * @param string
      * @return bool
      */
@@ -144,7 +144,7 @@ public static function isZeroPrefixed($value)
 
     /**
      * stripZero
-     * 
+     *
      * @param string $value
      * @return string
      */
@@ -159,7 +159,7 @@ public static function stripZero($value)
 
     /**
      * isNegative
-     * 
+     *
      * @param string
      * @return bool
      */
@@ -173,7 +173,7 @@ public static function isNegative($value)
 
     /**
      * isAddress
-     * 
+     *
      * @param string $value
      * @return bool true if the address is lowercase or in checksum format otherwise false
      */
@@ -243,7 +243,7 @@ public static function toChecksumAddress($value)
 
     /**
      * isHex
-     * 
+     *
      * @param string $value
      * @return bool
      */
@@ -255,7 +255,7 @@ public static function isHex($value)
     /**
      * sha3
      * keccak256
-     * 
+     *
      * @param string $value
      * @return string
      */
@@ -277,7 +277,7 @@ public static function sha3($value)
 
     /**
      * toString
-     * 
+     *
      * @param mixed $value
      * @return string
      */
@@ -292,9 +292,9 @@ public static function toString($value)
      * toWei
      * Change number from unit to wei.
      * For example:
-     * $wei = Utils::toWei('1', 'kwei'); 
+     * $wei = Utils::toWei('1', 'kwei');
      * $wei->toString(); // 1000
-     * 
+     *
      * @param BigNumber|string $number
      * @param string $unit
      * @return \phpseclib\Math\BigInteger
@@ -358,9 +358,9 @@ public static function toWei($number, $unit)
      * toEther
      * Change number from unit to ether.
      * For example:
-     * list($bnq, $bnr) = Utils::toEther('1', 'kether'); 
+     * list($bnq, $bnr) = Utils::toEther('1', 'kether');
      * $bnq->toString(); // 1000
-     * 
+     *
      * @param BigNumber|string|int $number
      * @param string $unit
      * @return array
@@ -380,9 +380,9 @@ public static function toEther($number, $unit)
      * fromWei
      * Change number from wei to unit.
      * For example:
-     * list($bnq, $bnr) = Utils::fromWei('1000', 'kwei'); 
+     * list($bnq, $bnr) = Utils::fromWei('1000', 'kwei');
      * $bnq->toString(); // 1
-     * 
+     *
      * @param BigNumber|string|int $number
      * @param string $unit
      * @return \phpseclib\Math\BigInteger
@@ -404,7 +404,7 @@ public static function fromWei($number, $unit)
 
     /**
      * jsonMethodToString
-     * 
+     *
      * @param stdClass|array $json
      * @return string
      */
@@ -450,7 +450,7 @@ public static function jsonMethodToString($json)
 
     /**
      * jsonToArray
-     * 
+     *
      * @param stdClass|array $json
      * @return array
      */
@@ -486,7 +486,7 @@ public static function jsonToArray($json)
     /**
      * toBn
      * Change number or number string to bignumber.
-     * 
+     *
      * @param BigNumber|string|int $number
      * @return array|\phpseclib\Math\BigInteger
      */
@@ -552,7 +552,7 @@ public static function toBn($number)
 
     /**
      * hexToNumber
-     * 
+     *
      * @param string $hexNumber
      * @return int
      */
@@ -563,4 +563,4 @@ public static function hexToNumber($hexNumber)
         }
         return intval(self::toBn($hexNumber)->toString());
     }
-}
\ No newline at end of file
+}
diff --git a/test/unit/BigNumberFormatterTest.php b/test/unit/BigNumberFormatterTest.php
index 87dc6216..48e5da3a 100644
--- a/test/unit/BigNumberFormatterTest.php
+++ b/test/unit/BigNumberFormatterTest.php
@@ -3,21 +3,21 @@
 namespace Test\Unit;
 
 use Test\TestCase;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 use Web3\Formatters\BigNumberFormatter;
 
-class BigNumberFormatterTest extends TestCase
+class BigNumberFormatterTest extends \PHPUnit\Framework\TestCase
 {
     /**
      * formatter
-     * 
+     *
      * @var \Web3\Formatters\BigNumberFormatter
      */
     protected $formatter;
 
     /**
      * setUp
-     * 
+     *
      * @return void
      */
     public function setUp(): void
@@ -28,7 +28,7 @@ public function setUp(): void
 
     /**
      * testFormat
-     * 
+     *
      * @return void
      */
     public function testFormat()
@@ -39,4 +39,4 @@ public function testFormat()
         $this->assertEquals($bigNumber->toString(), '1');
         $this->assertTrue($bigNumber instanceof BigNumber);
     }
-}
\ No newline at end of file
+}
diff --git a/test/unit/ContractTest.php b/test/unit/ContractTest.php
index 985a1a74..4e4243f6 100644
--- a/test/unit/ContractTest.php
+++ b/test/unit/ContractTest.php
@@ -8,7 +8,7 @@
 use Web3\Utils;
 use Web3\Contracts\Ethabi;
 use Web3\Formatters\IntegerFormatter;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 
 class ContractTest extends TestCase
 {
@@ -1631,4 +1631,4 @@ function () use ($promise2) { return $promise2; },
             function () use ($promise3) { return $promise3; },
         ]));
     }
-}
\ No newline at end of file
+}
diff --git a/test/unit/EthApiTest.php b/test/unit/EthApiTest.php
index f7645809..83f987f9 100644
--- a/test/unit/EthApiTest.php
+++ b/test/unit/EthApiTest.php
@@ -5,7 +5,7 @@
 use RuntimeException;
 use InvalidArgumentException;
 use Test\TestCase;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 
 class EthApiTest extends TestCase
 {
@@ -795,4 +795,4 @@ public function testWrongCallback()
 
         $eth->protocolVersion();
     }
-}
\ No newline at end of file
+}
diff --git a/test/unit/EthBatchTest.php b/test/unit/EthBatchTest.php
index 591f50e4..7584681e 100644
--- a/test/unit/EthBatchTest.php
+++ b/test/unit/EthBatchTest.php
@@ -4,7 +4,7 @@
 
 use RuntimeException;
 use Test\TestCase;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 
 class EthBatchTest extends TestCase
 {
@@ -74,4 +74,4 @@ public function testBatchAsync()
         $this->assertTrue($promise instanceof \React\Promise\PromiseInterface);
         \React\Async\await($promise);
     }
-}
\ No newline at end of file
+}
diff --git a/test/unit/NetApiTest.php b/test/unit/NetApiTest.php
index 0c96d571..db7871e9 100644
--- a/test/unit/NetApiTest.php
+++ b/test/unit/NetApiTest.php
@@ -5,7 +5,7 @@
 use RuntimeException;
 use InvalidArgumentException;
 use Test\TestCase;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 
 class NetApiTest extends TestCase
 {
@@ -132,4 +132,4 @@ public function testWrongCallback()
 
         $net->version();
     }
-}
\ No newline at end of file
+}
diff --git a/test/unit/NetBatchTest.php b/test/unit/NetBatchTest.php
index 9fadb1f8..8ee20a2d 100644
--- a/test/unit/NetBatchTest.php
+++ b/test/unit/NetBatchTest.php
@@ -4,7 +4,7 @@
 
 use RuntimeException;
 use Test\TestCase;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 
 class NetBatchTest extends TestCase
 {
@@ -78,4 +78,4 @@ public function testBatchAsync()
         $this->assertTrue($promise instanceof \React\Promise\PromiseInterface);
         \React\Async\await($promise);
     }
-}
\ No newline at end of file
+}
diff --git a/test/unit/UtilsTest.php b/test/unit/UtilsTest.php
index 76244edf..cb83d4b1 100644
--- a/test/unit/UtilsTest.php
+++ b/test/unit/UtilsTest.php
@@ -5,7 +5,7 @@
 use InvalidArgumentException;
 use stdClass;
 use Test\TestCase;
-use phpseclib\Math\BigInteger as BigNumber;
+use phpseclib3\Math\BigInteger as BigNumber;
 use Web3\Utils;
 use Web3\Contract;
 
@@ -652,4 +652,4 @@ public function testToBn()
         $this->expectException(InvalidArgumentException::class);
         $bn = Utils::toBn(new stdClass);
     }
-}
\ No newline at end of file
+}