diff --git a/lib/ASN1/ASNObject.php b/lib/ASN1/ASNObject.php
index 3b7f162..d338ad9 100644
--- a/lib/ASN1/ASNObject.php
+++ b/lib/ASN1/ASNObject.php
@@ -330,7 +330,14 @@ protected static function parseContentLength(&$binaryData, &$offsetIndex, $minim
                 if (strlen($binaryData) <= $offsetIndex) {
                     throw new ParserException('Can not parse content length (long form) from data: Offset index larger than input size', $offsetIndex);
                 }
-                $contentLength = $contentLength->shiftLeft(8)->add(ord($binaryData[$offsetIndex++]));
+                $octet = ord($binaryData[$offsetIndex++]);
+                if ($i === 0 && $octet === 0) {
+                    throw new ParserException('Content length cannot have leading zero bytes', $offsetIndex);
+                }
+                $contentLength = $contentLength->shiftLeft(8)->add($octet);
+            }
+            if ($nrOfLengthOctets < 2 && $contentLength->compare(0x80) < 0) {
+                throw new ParserException('Extended length used for short message', $offsetIndex);
             }
 
             if ($contentLength->compare(PHP_INT_MAX) > 0) {
diff --git a/lib/ASN1/AbstractTime.php b/lib/ASN1/AbstractTime.php
index 8e721ae..f67ef26 100644
--- a/lib/ASN1/AbstractTime.php
+++ b/lib/ASN1/AbstractTime.php
@@ -23,6 +23,9 @@ abstract class AbstractTime extends ASNObject
     public function __construct($dateTime = null, $dateTimeZone = 'UTC')
     {
         if ($dateTime == null || is_string($dateTime)) {
+            if (is_null($dateTime)) {
+                $dateTime = 'NOW';
+            }
             $timeZone = new DateTimeZone($dateTimeZone);
             $dateTimeObject = new DateTime($dateTime, $timeZone);
             if ($dateTimeObject == false) {
diff --git a/lib/ASN1/Universal/OctetString.php b/lib/ASN1/Universal/OctetString.php
index 5d69ae7..e12e722 100644
--- a/lib/ASN1/Universal/OctetString.php
+++ b/lib/ASN1/Universal/OctetString.php
@@ -47,18 +47,25 @@ public function getType()
 
     protected function calculateContentLength()
     {
+        if (is_null($this->value)) {
+            return 0;
+        }
         return strlen($this->value) / 2;
     }
 
     protected function getEncodedValue()
     {
         $value = $this->value;
+        if (is_null($value)) {
+            return '';
+        }
+        // This appears to expect hex strings but sometimes is populated by binary data
         $result = '';
 
-        //Actual content
+        // Actual content
         while (strlen($value) >= 2) {
-            // get the hex value byte by byte from the string and and add it to binary result
-            $result .= chr(hexdec(substr($value, 0, 2)));
+            // get the hex value byte by byte from the string and add it to binary result
+            $result .= @chr(hexdec(substr($value, 0, 2)));
             $value = substr($value, 2);
         }
 
@@ -67,6 +74,9 @@ protected function getEncodedValue()
 
     public function getContent()
     {
+        if (is_null($this->value)) {
+            return '';
+        }
         return strtoupper($this->value);
     }
 
diff --git a/tests/ASN1/ObjectTest.php b/tests/ASN1/ObjectTest.php
index 9649948..114d3e2 100644
--- a/tests/ASN1/ObjectTest.php
+++ b/tests/ASN1/ObjectTest.php
@@ -321,6 +321,22 @@ public function testFromBinaryExceedsMaxInt()
         ASNObject::fromBinary($bin);
     }
 
+    public function testWithLeadingZeroes()
+    {
+        $this->expectException(ParserException::class);
+        $this->expectExceptionMessage("ASN.1 Parser Exception at offset 3: Content length cannot have leading zero bytes");
+        $bin = hex2bin('30820066023100814cc9a70febda342d4ada87fc39426f403d5e89808428460c1eca60c897bfd6728da14673854673d7d297ea944a15e202310084f5ef11d22f22d0548af6a50dbf2f6a1bb9054585af5e600c49cf35b1e69b712754dd781c837355ddd41c752193a7cd');
+        ASNObject::fromBinary($bin);
+    }
+
+    public function testExtendedFormShortLength()
+    {
+        $this->expectException(ParserException::class);
+        $this->expectExceptionMessage('ASN.1 Parser Exception at offset 3: Extended length used for short message');
+        $bin = hex2bin('30814502202ba3a8be6b94d5ec80a6d9d1190a436effe50d85a1eee859b8cc6af9bd5c2e18022100b329f479a2bbd0a5c384ee1493b1f5186a87139cac5df4087c134b49156847db');
+        ASNObject::fromBinary($bin);
+    }
+
     /**
      * @depends testFromBinary
      */