A PHP library for X.690 Abstract Syntax Notation One (ASN.1) Distinguished Encoding Rules (DER) encoding and decoding.

This library is available on Packagist.

composer require sop/asn1

The general idea is that each ASN.1 type has its corresponding PHP class, that knows the details of encoding and decoding the specific type.

To decode DER data, use fromDER static method of the expected type. To encode object to DER, use toDER instance method.

All objects are immutable and method chaining is promoted for the fluency of the API. Exception shall be thrown on errors.

Here are some simple usage examples. Namespaces are omitted for brevity.

Encode a sequence containing a UTF-8 string, an integer and an explicitly tagged object identifier.

$seq = new Sequence(
    new UTF8String("Hello"),
    new Integer(42),
    new ExplicitlyTaggedType(
        1, new ObjectIdentifier("1.3.6.1.3"))
);
$der = $seq->toDER();
echo bin2hex($der);

Outputs:

30120c0548656c6c6f02012aa10606042b060103

Decode DER encoding from above.

$seq = Sequence::fromDER($der);
echo $seq->at(0)->asUTF8String()->string() . "\n";
echo $seq->at(1)->asInteger()->number() . "\n";
echo $seq->at(2)->asTagged()->asExplicit()
    ->asObjectIdentifier()->oid() . "\n";

Outputs:

Hello
42
1.3.6.1.3

See the following for more practical real-world usage examples.

• EC Private Key
  • Decode
  • Encode
• X.501 Attribute
  • Decode
  • Encode
• X.509 Certificate (TBSCertificate sequence)
  • Decode
  • Encode

This project is licensed under the MIT License.