diff --git a/phpseclib/File/ASN1.php b/phpseclib/File/ASN1.php
index 9c85083d..da70d415 100644
--- a/phpseclib/File/ASN1.php
+++ b/phpseclib/File/ASN1.php
@@ -509,7 +509,7 @@ class File_ASN1
      */
     function asn1map($decoded, $mapping, $special = array())
     {
-        if (isset($mapping['explicit'])) {
+        if (isset($mapping['explicit']) && is_array($decoded['content'])) {
             $decoded = $decoded['content'][0];
         }
 
@@ -550,7 +550,15 @@ class File_ASN1
             case $decoded['type'] == $mapping['type']:
                 break;
             default:
-                return null;
+                // if $decoded['type'] and $mapping['type'] are both strings, but different types of strings,
+                // let it through
+                switch (true) {
+                    case $decoded['type'] < 18: // FILE_ASN1_TYPE_NUMERIC_STRING == 18
+                    case $decoded['type'] > 30: // FILE_ASN1_TYPE_BMP_STRING == 30
+                    case $mapping['type'] < 18:
+                    case $mapping['type'] > 30:
+                        return null;
+                }
         }
 
         if (isset($mapping['implicit'])) {
@@ -972,6 +980,10 @@ class File_ASN1
                         }
                     }
 
+                    if (isset($mapping['min']) && $mapping['min'] >= 1 && $size < $mapping['min']) {
+                        $size = $mapping['min'] - 1;
+                    }
+
                     $offset = 8 - (($size + 1) & 7);
                     $offset = $offset !== 8 ? $offset : 0;
 
@@ -1085,7 +1097,12 @@ class File_ASN1
         }
 
         if (isset($mapping['cast'])) {
-            $tag = ($mapping['class'] << 6) | ($tag & 0x20) | $mapping['cast'];
+            if (isset($mapping['explicit']) || $mapping['type'] == FILE_ASN1_TYPE_CHOICE) {
+                $value = chr($tag) . $this->_encodeLength(strlen($value)) . $value;
+                $tag = ($mapping['class'] << 6) | 0x20 | $mapping['cast'];
+            } else {
+                $tag = ($mapping['class'] << 6) | (ord($temp[0]) & 0x20) | $mapping['cast'];
+            }
         }
 
         return chr($tag) . $this->_encodeLength(strlen($value)) . $value;
diff --git a/tests/File/ASN1/DevTest.php b/tests/File/ASN1/DevTest.php
new file mode 100644
index 00000000..edfc450f
--- /dev/null
+++ b/tests/File/ASN1/DevTest.php
@@ -0,0 +1,236 @@
+<?php
+/**
+ * @author    Jim Wigginton <terrafrost@php.net>
+ * @copyright MMXIV Jim Wigginton
+ * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
+ */
+
+require_once 'File/ASN1.php';
+
+class File_ASN1_DevTest extends PhpseclibTestCase
+{
+    /**
+    * on older versions of File_ASN1 this would yield a PHP Warning
+    * @group github275
+    */
+    public function testAnyString()
+    {
+        $KDC_REP = array(
+            'type' => FILE_ASN1_TYPE_SEQUENCE,
+            'children' => array(
+                 'pvno' => array(
+                    'constant' => 0,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY),
+                'msg-type' => array(
+                    'constant' => 1,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY),
+                'padata' => array(
+                    'constant' => 2,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY),
+                'crealm' => array(
+                    'constant' => 3,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY),
+                'cname' => array(
+                    'constant' => 4,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY),
+                'ticket' => array(
+                    'constant' => 5,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY),
+                'enc-part' => array(
+                    'constant' => 6,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY)
+            )
+        );
+
+        $AS_REP = array(
+            'class'    => FILE_ASN1_CLASS_APPLICATION,
+            'cast'     => 11,
+            'optional' => true,
+            'explicit' => true
+        ) + $KDC_REP;
+
+        $str = 'a4IC3jCCAtqgAwIBBaEDAgELoi8wLTAroQMCAROiJAQiMCAwHqADAgEXoRcbFUNSRUFUVUlUWS5ORVR0ZXN0dXNlcqMPGw' . 
+               '1DUkVBVFVJVFkuTkVUpBUwE6ADAgEBoQwwChsIdGVzdHVzZXKlggFOYYIBSjCCAUagAwIBBaEPGw1DUkVBVFVJVFkuTkVU' .
+               'oiIwIKADAgECoRkwFxsGa3JidGd0Gw1DUkVBVFVJVFkuTkVUo4IBCDCCAQSgAwIBF6EDAgEBooH3BIH0AQlxgm/j4z74Ki' .
+               'GsJJnROhh8JAiN7pdvlnkxCYKdG6UgdfK/K0NZ+yz+Xg4kgFO1cQ4XYT4Fm3MTmOHzlFmbzlVkUqBI/RnWA9YTREC9Q7Mf' .
+               'PPYfRxRG/C6FlahxHCOKj9GUj7bXg7Oq3Sm+QsKTS2bZT05biNf1s7tPCkdIOO0AAd7hvTCpTNAKl+OLN4cpA6pwwk5c3h' .
+               '58Ce5/Uri5yBmrfwgkCD5AJUAI/WH56SEEvpifLc6C96w/7y2krAiZm5PyEO0HVhTzUjKGSHoSMb+Z3HI/ul+G9z0Z4qDu' .
+               'NjvgP0jKdrKiwWN00NjpiQ0byZd4y6aCASEwggEdoAMCAReiggEUBIIBEHyi8DIbdcfw2DpniBJ3Sh8dDaEbQx+gWx3omC' .
+               'TBEyts4sQGTwgQcqkWfeer8M+SkZs/GGZq2YYkyeF+9b6TxlYuX145NuB3KcyzaS7VNrX37E5nGgG8K6r5gTFOhLCqsjjv' .
+               'gPXXqLeJo5D1nV+c8BPIEVsu/bbBPgSqpDwUs2mX1WkEg5vfb7kZMC8+LHiRy+sItvIiTtxxEsQ/GEF/ono3hZrEnDa/C+' .
+               '4P3wep6uNMLnLzXJmUaAMaopjE+MOcai/t6T9Vg4pERF5Waqwg5ibAbVGK19HuS4LiKiaY3JsyYBuNkEDwiqM7i1Ekw3V+' .
+               '+zoEIxqgXjGgPdrWkzU/H6rnXiqMtiZZqUXwWY0zkCmy';
+
+        $asn1 = new File_ASN1();
+        $decoded = $asn1->decodeBER(base64_decode($str));
+        $result = $asn1->asn1map($decoded[0], $AS_REP);
+
+        $this->assertInternalType('array', $result);
+    }
+
+    /**
+    * on older versions of File_ASN1 this would produce a null instead of an array
+    * @group github275
+    */
+    public function testIncorrectString()
+    {
+        $PA_DATA = array(
+            'type' => FILE_ASN1_TYPE_SEQUENCE,
+            'children' => array(
+                'padata-type' => array(
+                    'constant' => 1,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_INTEGER
+                ),
+                'padata-value' => array(
+                    'constant' => 2,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_OCTET_STRING
+                )
+            )
+        );
+
+        $PrincipalName = array(
+            'type' => FILE_ASN1_TYPE_SEQUENCE,
+            'children' => array(
+                'name-type' => array(
+                    'constant' => 0,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_INTEGER
+                ),
+                'name-string' => array(
+                    'constant' => 1,
+                    'optional' => true,
+                    'explicit' => true,
+                    'min' => 0,
+                    'max' => -1,
+                    'type' => FILE_ASN1_TYPE_SEQUENCE,
+                    'children' => array('type' => FILE_ASN1_TYPE_IA5_STRING) // should be FILE_ASN1_TYPE_GENERAL_STRING
+                )
+            )
+        );
+
+        $Ticket = array(
+            'class'    => FILE_ASN1_CLASS_APPLICATION,
+            'cast'     => 1,
+            'optional' => true,
+            'explicit' => true,
+            'type' => FILE_ASN1_TYPE_SEQUENCE,
+            'children' => array(
+                'tkt-vno' => array(
+                    'constant' => 0,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_INTEGER
+                ),
+                'realm' => array(
+                    'constant' => 1,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY
+                ),
+                'sname' => array(
+                    'constant' => 2,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY
+                ),
+                'enc-part' => array(
+                    'constant' => 3,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY
+                )
+            )
+        );
+
+        $KDC_REP = array(
+            'type' => FILE_ASN1_TYPE_SEQUENCE,
+            'children' => array(
+                'pvno' => array(
+                    'constant' => 0,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_INTEGER),
+                'msg-type' => array(
+                     'constant' => 1,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_INTEGER),
+                'padata' => array(
+                    'constant' => 2,
+                    'optional' => true,
+                    'explicit' => true,
+                    'min' => 0,
+                    'max' => -1,
+                    'type' => FILE_ASN1_TYPE_SEQUENCE,
+                    'children' => $PA_DATA),
+                'crealm' => array(
+                    'constant' => 3,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_OCTET_STRING),
+                'cname' => array(
+                    'constant' => 4,
+                    'optional' => true,
+                    'explicit' => true) + $PrincipalName,
+                    //'type' => FILE_ASN1_TYPE_ANY),
+                'ticket' => array(
+                    'constant' => 5,
+                    'optional' => true,
+                    'implicit' => true,
+                    'min' => 0,
+                    'max' => 1,
+                    'type' => FILE_ASN1_TYPE_SEQUENCE,
+                    'children' => $Ticket),
+                'enc-part' => array(
+                    'constant' => 6,
+                    'optional' => true,
+                    'explicit' => true,
+                    'type' => FILE_ASN1_TYPE_ANY)
+            )
+        );
+
+        $AS_REP = array(
+            'class'    => FILE_ASN1_CLASS_APPLICATION,
+            'cast'     => 11,
+            'optional' => true,
+            'explicit' => true
+        ) + $KDC_REP;
+
+        $str = 'a4IC3jCCAtqgAwIBBaEDAgELoi8wLTAroQMCAROiJAQiMCAwHqADAgEXoRcbFUNSRUFUVUlUWS5ORVR0ZXN0dXNlcqMPGw' . 
+               '1DUkVBVFVJVFkuTkVUpBUwE6ADAgEBoQwwChsIdGVzdHVzZXKlggFOYYIBSjCCAUagAwIBBaEPGw1DUkVBVFVJVFkuTkVU' .
+               'oiIwIKADAgECoRkwFxsGa3JidGd0Gw1DUkVBVFVJVFkuTkVUo4IBCDCCAQSgAwIBF6EDAgEBooH3BIH0AQlxgm/j4z74Ki' .
+               'GsJJnROhh8JAiN7pdvlnkxCYKdG6UgdfK/K0NZ+yz+Xg4kgFO1cQ4XYT4Fm3MTmOHzlFmbzlVkUqBI/RnWA9YTREC9Q7Mf' .
+               'PPYfRxRG/C6FlahxHCOKj9GUj7bXg7Oq3Sm+QsKTS2bZT05biNf1s7tPCkdIOO0AAd7hvTCpTNAKl+OLN4cpA6pwwk5c3h' .
+               '58Ce5/Uri5yBmrfwgkCD5AJUAI/WH56SEEvpifLc6C96w/7y2krAiZm5PyEO0HVhTzUjKGSHoSMb+Z3HI/ul+G9z0Z4qDu' .
+               'NjvgP0jKdrKiwWN00NjpiQ0byZd4y6aCASEwggEdoAMCAReiggEUBIIBEHyi8DIbdcfw2DpniBJ3Sh8dDaEbQx+gWx3omC' .
+               'TBEyts4sQGTwgQcqkWfeer8M+SkZs/GGZq2YYkyeF+9b6TxlYuX145NuB3KcyzaS7VNrX37E5nGgG8K6r5gTFOhLCqsjjv' .
+               'gPXXqLeJo5D1nV+c8BPIEVsu/bbBPgSqpDwUs2mX1WkEg5vfb7kZMC8+LHiRy+sItvIiTtxxEsQ/GEF/ono3hZrEnDa/C+' .
+               '4P3wep6uNMLnLzXJmUaAMaopjE+MOcai/t6T9Vg4pERF5Waqwg5ibAbVGK19HuS4LiKiaY3JsyYBuNkEDwiqM7i1Ekw3V+' .
+               '+zoEIxqgXjGgPdrWkzU/H6rnXiqMtiZZqUXwWY0zkCmy';
+
+        $asn1 = new File_ASN1();
+        $decoded = $asn1->decodeBER(base64_decode($str));
+        $result = $asn1->asn1map($decoded[0], $AS_REP);
+
+        $this->assertInternalType('array', $result);
+    }
+}