asn1
Python-ASN1 is a simple ASN.1 encoder and decoder for Python 2.7+ and 3.5+.
Decision gist · record as of 2026-08-14
Yes. The package is actively maintained, has no known vulnerabilities, carries a permissive MIT license, and installs with minimal friction. It is suitable for any project needing ASN.1 encoding/decoding in pure Python across a wide range of Python versions.AI-flagged interpretation of the facts on this page — verify before relying
Before you install
- Low install friction with a single pure-Python runtime dependency (enum-compat).
- Actively maintained with a recent release and no known vulnerabilities.
License · maintenance · safety
MIT (permissive) — MIT license permits unrestricted use, modification, and distribution in both open-source and proprietary projects with minimal obligations.
last release 2026-05-15 (91 days) · last repo commit 2026-05-15 · 110 stars
0 known vulnerabilities (OSV.dev, 2026-08-14) · 1,747,756 downloads/mo, #3,595 on PyPI
Alternatives
Verify before relying
pip install asn1
import asn1
encoder = asn1.Encoder()
encoder.start()
encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)
encoded_bytes = encoder.output()
decoder = asn1.Decoder()
decoder.start(encoded_bytes)
tag, value = decoder.read()- Whether enum-compat is available for all supported Python versions (2.7, 3.5–3.14)
- Performance characteristics when encoding/decoding large or deeply nested structures
- Use in certificate and cryptographic applications beyond what the fact sheet documents
What it is and what it does
Python-ASN1 is a pure-Python library for encoding and decoding ASN.1 data structures, the standard format used in cryptography, network protocols, and structured data interchange. It supports both BER (parser) and DER (parser and generator) encoding formats, including indefinite lengths, and handles most common ASN.1 types including REAL values. The library is designed to be lightweight and portable—it can be integrated by simply including a file in your project or installed via pip.
The package provides two main interfaces: an Encoder class for converting Python data into ASN.1 binary format, and a Decoder class for parsing ASN.1 bytes back into readable values. Recent versions add context-manager support for cleaner resource handling and comply with ASN.1:2008 standards. It targets Python 2.7 and 3.5 through 3.14, relying only on enum-compat as a runtime dependency.
Use it for
- Encode and decode structured data in network protocols that use ASN.1 serialization
- Work with Object Identifiers (OIDs) and other ASN.1 primitives in protocol implementations
- Integrate ASN.1 handling into legacy Python 2.7 systems without external C dependencies
- Parse and generate ASN.1-encoded messages in compliance testing or protocol analysis
- Build tools that transform ASN.1-encoded data across different encoding formats
Worth the install?
AI-flagged interpretation of the facts on this page. Verify before relying on it.
Yes.
The package is actively maintained, has no known vulnerabilities, carries a permissive MIT license, and installs with minimal friction. It is suitable for any project needing ASN.1 encoding/decoding in pure Python across a wide range of Python versions.
Install
asn1 on PyPI
Before you install
Low install friction with a single pure-Python runtime dependency (enum-compat). Actively maintained with a recent release and no known vulnerabilities.
License in practice
MIT license permits unrestricted use, modification, and distribution in both open-source and proprietary projects with minimal obligations.
Quickstart
pip install asn1
import asn1
encoder = asn1.Encoder()
encoder.start()
encoder.write('1.2.3', asn1.Numbers.ObjectIdentifier)
encoded_bytes = encoder.output()
decoder = asn1.Decoder()
decoder.start(encoded_bytes)
tag, value = decoder.read()Verify before relying
- Whether enum-compat is available for all supported Python versions (2.7, 3.5–3.14)
- Performance characteristics when encoding/decoding large or deeply nested structures
- Use in certificate and cryptographic applications beyond what the fact sheet documents
Package facts
| License | MIT permissive |
| Python support | Not specified |
| Install friction | Low. Pure-Python wheel |
| Runtime dependencies | 1 packageenum-compat |
| Maintenance | Actively maintained 91 days since the last release |
| Last repo commit | |
| First released | |
| Downloads | 1,747,756 / month, #3,595 on PyPI 30-day window, as of 2026-08-14 |
| Known vulnerabilities | None known OSV.dev, checked 2026-08-14 |
| Classifiers | Development Status :: 5 - Production/StableIntended Audience :: DevelopersOperating System :: Microsoft :: WindowsOperating System :: POSIXOperating System :: UnixProgramming Language :: PythonProgramming Language :: Python :: 2.7Programming Language :: Python :: 3Programming Language :: Python :: 3.10Programming Language :: Python :: 3.11Programming Language :: Python :: 3.12Programming Language :: Python :: 3.13Programming Language :: Python :: 3.14Programming Language :: Python :: 3.5Programming Language :: Python :: 3.6Programming Language :: Python :: 3.7Programming Language :: Python :: 3.8Programming Language :: Python :: 3.9Programming Language :: Python :: Implementation :: CPythonProgramming Language :: Python :: Implementation :: PyPyTopic :: Utilities |
Evidence: asn1-3.3.0-py2.py3-none-any.whl
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See also asn1tools · pyasn1 · x690 · asn1crypto · bencode.py · types-pyasn1 · json-numpy · mutf8 · py-multibase · databento-dbn