diff --git a/src/Util/Crypto.php b/src/Util/Crypto.php
index 785860c182..7dd0dee5c0 100644
--- a/src/Util/Crypto.php
+++ b/src/Util/Crypto.php
@@ -483,21 +483,16 @@ class Crypto
 	 *
 	 * @param string $digits The count of digits
 	 * @return int The random Digits
+	 *
+	 * @throws \Exception In case 'random_int' isn't usable
 	 */
 	public static function randomDigits($digits)
 	{
 		$rn = '';
 
-		if (!function_exists('random_int')) {
-			// using rand() function for PHP 5.x compatibility
-			for ($i = 0; $i < $digits; $i++) {
-				$rn .= rand(0, 9);
-			}
-		} else {
-			// generating cryptographically secure pseudo-random integers
-			for ($i = 0; $i < $digits; $i++) {
-				$rn .= random_int(0, 9);
-			}
+		// generating cryptographically secure pseudo-random integers
+		for ($i = 0; $i < $digits; $i++) {
+			$rn .= random_int(0, 9);
 		}
 
 		return $rn;
diff --git a/tests/src/Util/CryptoTest.php b/tests/src/Util/CryptoTest.php
index 7c6af0070c..b976a09838 100644
--- a/tests/src/Util/CryptoTest.php
+++ b/tests/src/Util/CryptoTest.php
@@ -7,24 +7,6 @@ use PHPUnit\Framework\TestCase;
 
 class CryptoTest extends TestCase
 {
-	/**
-	 * Replaces function_exists results with given mocks
-	 *
-	 * @param array $functions a list from function names and their result
-	 */
-	private function setFunctions($functions)
-	{
-		global $phpMock;
-		$phpMock['function_exists'] = function($function) use ($functions) {
-			foreach ($functions as $name => $value) {
-				if ($function == $name) {
-					return $value;
-				}
-			}
-			return '__phpunit_continue__';
-		};
-	}
-
 	/**
 	 * Replaces rand results with given mocks
 	 *
@@ -53,24 +35,8 @@ class CryptoTest extends TestCase
 		};
 	}
 
-	public function testRandomDigitsRand()
-	{
-		$this->setFunctions(['random_int' => false]);
-		$this->assertRand(0, 9);
-
-		$test = Crypto::randomDigits(1);
-		$this->assertEquals(1, strlen($test));
-		$this->assertEquals(1, $test);
-
-		$test = Crypto::randomDigits(8);
-		$this->assertEquals(8, strlen($test));
-		$this->assertEquals(11111111, $test);
-	}
-
-
 	public function testRandomDigitsRandomInt()
 	{
-		$this->setFunctions(['random_int' => true]);
 		$this->assertRandomInt(0, 9);
 
 		$test = Crypto::randomDigits(1);
@@ -83,39 +49,6 @@ class CryptoTest extends TestCase
 	}
 }
 
-/**
- * A workaround to replace the PHP native function_exists() with a mocked function
- *
- * @param string $function_name the Name of the function
- *
- * @return bool true or false
- */
-function function_exists($function_name)
-{
-	global $phpMock;
-	if (isset($phpMock['function_exists'])) {
-		$result = call_user_func_array($phpMock['function_exists'], func_get_args());
-		if ($result !== '__phpunit_continue__') {
-			return $result;
-		}
-	}
-	return call_user_func_array('\function_exists', func_get_args());
-}
-
-/**
- * A workaround to replace the PHP native rand() (< 7.0) with a mocked function
- *
- * @return int
- */
-function rand($min, $max)
-{
-	global $phpMock;
-	if (isset($phpMock['rand'])) {
-		$result = call_user_func_array($phpMock['rand'], func_get_args());
-		return $result;
-	}
-}
-
 /**
  * A workaround to replace the PHP native random_int() (>= 7.0) with a mocked function
  *