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Python-ASN1 is a simple ASN.1 encoder and decoder for Python 2.7+ and 3.5+.

Project description

Python-ASN1 is a simple ASN.1 encoder and decoder for Python 2.7 and 3.5+.


  • Support BER (parser) and DER (parser and generator) encoding

  • 100% python, compatible with version 2.6, 2.7, 3.3 and higher

  • Can be integrated by just including a file into your project


Python-ASN1 relies on Python-Future for Python 2 and 3 compatibility. To install Python-Future:

pip install future

How to install Python-asn1

Install from PyPi with the following:

pip install asn1

or download the repository from GitHub and install with the following:

python install

You can also simply include into your project.

How to use Python-asn1


If you want to encode data and retrieve its DER-encoded representation, use code such as:

import asn1

encoder = asn1.Encoder()
encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)
encoded_bytes = encoder.output()


If you want to decode ASN.1 from DER or BER encoded bytes, use code such as:

import asn1

decoder = asn1.Decoder()
tag, value =


The complete documentation is available on Read The Docs:


Python-ASN1 is free software that is made available under the MIT license. Consult the file LICENSE that is distributed together with this library for the exact licensing terms.


2.3.0 (2020-04-05)

  • Tests: Replace nose by pytest

  • Add Python 3.8, remove Python 3.4 support

  • PR#26 (from rumbah): Add test for default (implicit) encoding types

  • PR#25 (from thomwiggers): Attempt to support BIT STRING

  • Fix wrong example code, see #27

  • (from jcrowgey) Makes the package usable with pip install

  • Remove support of Python 3.3 (some dependencies do not support 3.3)

  • PR#15 (from ThePlasmaRailgun) Fix parsing of object identifier

  • PR#10 (from robinleander): Allow user to determine decoding tagtype

2.2.0 (2017-10-30)

  • Use “true” enums instead of classes. Use enun34 backport for old Python versions.

2.1.1 (2017-10-30)

  • Fix a bug (#9): two’s complement corner case with values such as -32769. Add new test cases to test them.

2.1.0 (2016-12-18)

  • Add more documentation

  • Use (simulated) enumerations

  • Add Python 2.6 in automated checks and tests

  • Add type hints (for static checking) and fix some code

2.0.0 (2016-12-16)

  • First public release by Sebastien Andrivet

  • Support both python 2 and 3 (with Python-Future)

  • All strings are now in unicode

  • Add more ASN.1 tags (like PrintableString)

  • Fix errors in the example (

  • Code reorganization

0.9 (2011-05-18)

  • Initial public release by Geert Jansen

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