ASN.1 Parser for Dart

https://github.com/wstrange/asn1lib
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An ASN.1 library for Dart that encodes and decodes ASN.1 Objects to/from BER bytes.
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License:BSD-3-Clause
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### Inspect RSA Private Key Details

Source: https://github.com/wstrange/asn1lib/blob/master/test/resource/README.md

Extracts and displays detailed information about an RSA private key from an PEM file. Use this to verify key properties or extract public components.

```bash
openssl rsa -in rsa_private_key.pem -text -noout -out rsa_private_key.txt
```

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### Generate RSA Private Key

Source: https://github.com/wstrange/asn1lib/blob/master/test/resource/README.md

Generates an RSA private key and saves it to an PEM file. This command is the first step in many cryptographic operations.

```bash
openssl genrsa -out rsa_private_key.pem
```

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### Decoding ASN.1 Sequence with Relaxed Parsing

Source: https://github.com/wstrange/asn1lib/blob/master/README.md

Demonstrates decoding using relaxed parsing, which allows for handling unsupported structures by returning a generic ASN1Object instead of throwing an error.

```dart
// relaxed parsing, returning a generic ASN1Object from (yet) unsupported structures, instead of throwing
var p2 = ASN1Parser(bytes, relaxedParsing: true);
var s3 = p2.nextObject();
// s3 is a sequence...
```

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### Encoding ASN.1 Sequence

Source: https://github.com/wstrange/asn1lib/blob/master/README.md

Demonstrates how to create and encode an ASN.1 sequence containing an integer, an octet string, and a boolean.

```dart
import 'package:asn1lib/asn1lib.dart';

var s = ASN1Sequence();
s.add(ASN1Integer(23));
s.add(ASN1OctetString('This is a test'));
s.add(ASN1Boolean(true));

// GET the BER Stream
var bytes = s
.
encodedBytes;
```

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### Decoding ASN.1 Sequence with Default Parsing

Source: https://github.com/wstrange/asn1lib/blob/master/README.md

Shows how to decode a BER-encoded byte stream into an ASN.1 object using the default parser.

```dart
import 'package:asn1lib/asn1lib.dart';

// e.g. bytes from the Encoding Example
var p = ASN1Parser(bytes);
var s2 = p.nextObject();
// s2 is a sequence...
```

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### Casting ASN.1 Context-Specific to ASN.1 Sequence

Source: https://github.com/wstrange/asn1lib/blob/master/README.md

Illustrates how to handle and 'recast' an ASN.1 context-specific object to a specific type like ASN1Sequence if its content is known.

```dart
    var s = parser.nextObject();
    // We expect this is a context-specific class
    expect(s, isA<ASN1ContextSpecific>());
    // which is also an ASN1Object...
    expect(s, isA<ASN1Object>());
    // We expect this is a sequence, so "recast" to a sequence type
    var sequence = ASN1Sequence.fromBytes(s.encodedBytes);
    expect(sequence, isA<ASN1Sequence>());
```

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### Encoding ASN.1 Octet String with UTF-16

Source: https://github.com/wstrange/asn1lib/blob/master/README.md

Shows how to explicitly encode an ASN.1 Octet String using UTF-16 encoding by converting the string to a Uint8List first.

```dart
var x = ASN1OctetString(Uint8List.fromList('some string'.codeUnits));
// new getter
var y = x.utf16StringValue;
```
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