dotnetframework/System.Formats.Asn1v9.0.2

About

Provides functionality for parsing, encoding, and decoding data using Abstract Syntax Notation One (ASN.1). ASN.1 is a standard interface description language for defining data structures that can be serialized and deserialized in a cross-platform way.

Key Features

• Parse ASN.1 data into .NET types.
• Encode .NET types into ASN.1 format.
• Support for BER, CER, DER: Handles Basic Encoding Rules (BER), Canonical Encoding Rules (CER), and Distinguished Encoding Rules (DER).

How to Use

Parsing ASN.1 data:

using System.Formats.Asn1; using System.Numerics; // Sample ASN.1 encoded data (DER format) byte[] asn1Data = [0x30, 0x09, 0x02, 0x01, 0x01, 0x02, 0x01, 0x02, 0x02, 0x01, 0x03]; // Create an AsnReader to parse the data AsnReader reader = new(asn1Data, AsnEncodingRules.DER); // Parse the sequence AsnReader sequenceReader = reader.ReadSequence(); // Read integers from the sequence BigInteger firstInt = sequenceReader.ReadInteger(); BigInteger secondInt = sequenceReader.ReadInteger(); BigInteger thirdInt = sequenceReader.ReadInteger(); Console.WriteLine($"First integer: {firstInt}"); Console.WriteLine($"Second integer: {secondInt}"); Console.WriteLine($"Third integer: {thirdInt}"); // First integer: 1 // Second integer: 2 // Third integer: 3

Decoding ASN.1 data using AsnDecoder:

using System.Formats.Asn1; using System.Numerics; using System.Text; // Sample ASN.1 encoded data byte[] booleanData = [0x01, 0x01, 0xFF]; // BOOLEAN TRUE byte[] integerData = [0x02, 0x01, 0x05]; // INTEGER 5 byte[] octetStringData = [0x04, 0x03, 0x41, 0x42, 0x43]; // OCTET STRING "ABC" byte[] objectIdentifierData = [0x06, 0x03, 0x2A, 0x03, 0x04]; // OBJECT IDENTIFIER 1.2.3.4 byte[] utf8StringData = [0x0C, 0x05, 0x48, 0x65, 0x6C, 0x6C, 0x6F]; // UTF8String "Hello" int bytesConsumed; bool booleanValue = AsnDecoder.ReadBoolean(booleanData, AsnEncodingRules.DER, out bytesConsumed); Console.WriteLine($"Decoded BOOLEAN value: {booleanValue}, Bytes consumed: {bytesConsumed}"); // Decoded BOOLEAN value: True, Bytes consumed: 3 BigInteger integerValue = AsnDecoder.ReadInteger(integerData, AsnEncodingRules.DER, out bytesConsumed); Console.WriteLine($"Decoded INTEGER value: {integerValue}, Bytes consumed: {bytesConsumed}"); // Decoded INTEGER value: 5, Bytes consumed: 3 byte[] octetStringValue = AsnDecoder.ReadOctetString(octetStringData, AsnEncodingRules.DER, out bytesConsumed); Console.WriteLine($"Decoded OCTET STRING value: {Encoding.ASCII.GetString(octetStringValue)}, Bytes consumed: {bytesConsumed}"); // Decoded OCTET STRING value: ABC, Bytes consumed: 5 string objectIdentifierValue = AsnDecoder.ReadObjectIdentifier(objectIdentifierData, AsnEncodingRules.DER, out bytesConsumed); Console.WriteLine($"Decoded OBJECT IDENTIFIER value: {objectIdentifierValue}, Bytes consumed: {bytesConsumed}"); // Decoded OBJECT IDENTIFIER value: 1.2.3.4, Bytes consumed: 5 string utf8StringValue = AsnDecoder.ReadCharacterString(utf8StringData, AsnEncodingRules.DER, UniversalTagNumber.UTF8String, out bytesConsumed); Console.WriteLine($"Decoded UTF8String value: {utf8StringValue}, Bytes consumed: {bytesConsumed}"); // Decoded UTF8String value: Hello, Bytes consumed: 7