asn1crypto

1.5.1 verified Tue May 12 auth: no python install: verified quickstart: stale

A fast, pure Python library for parsing and serializing ASN.1 structures, including private keys, public keys, certificates, and various PKCS standards. Current version: 1.5.1. Release cadence: irregular, with the latest release on March 15, 2022. ([pypi.org](https://pypi.org/project/asn1crypto/?utm_source=openai))

pip install asn1crypto

Common errors

error ModuleNotFoundError: No module named 'asn1crypto' ↓

cause The 'asn1crypto' package is not installed in the Python environment.

fix

Install the package using pip: 'pip install asn1crypto'.

error ImportError: cannot import name 'core' from 'asn1crypto' ↓

cause The 'core' module is not available in the 'asn1crypto' package, possibly due to an outdated version.

fix

Upgrade to the latest version of 'asn1crypto' using pip: 'pip install --upgrade asn1crypto'.

error AttributeError: module 'asn1crypto' has no attribute 'x509' ↓

cause The 'x509' module is not present in the 'asn1crypto' package, likely due to an incorrect import statement.

fix

Ensure the correct import statement: 'from asn1crypto import x509'.

error TypeError: 'NoneType' object is not subscriptable ↓

cause Attempting to access an element of a 'None' object, possibly due to a failed parsing operation.

fix

Check if the parsing operation returned 'None' and handle the error accordingly.

error ValueError: Invalid ASN.1 tag ↓

cause The input data contains an invalid ASN.1 tag, leading to a parsing error.

fix

Verify the input data for correctness and ensure it conforms to the expected ASN.1 structure.

Warnings

breaking The 'x509' module was introduced in version 0.22.0. Ensure your version is up-to-date to use this module. ↓

fix Upgrade to the latest version of asn1crypto.

gotcha When parsing certificates, ensure the input data is in DER format. PEM format requires base64 decoding before parsing. ↓

fix Convert PEM to DER format before parsing or use appropriate methods to handle PEM format.

breaking The script failed because 'certificate.pem' was not found. Ensure the certificate file exists in the expected path. ↓

fix Ensure the 'certificate.pem' file is present in the working directory or provide the correct absolute/relative path to the file.

breaking The script failed because 'certificate.pem' was not found. Ensure the certificate file exists in the expected location and has the correct permissions. ↓

fix Provide the 'certificate.pem' file in the script's execution directory or update the file path in the script to point to the correct location of the certificate file.

Install compatibility verified last tested: 2026-05-12

python os / libc status wheel install import disk

3.10 alpine (musl) - - 0.07s 18.7M

3.10 slim (glibc) - - 0.05s 19M

3.11 alpine (musl) - - 0.15s 20.7M

3.11 slim (glibc) - - 0.12s 21M

3.12 alpine (musl) - - 0.10s 12.6M

3.12 slim (glibc) - - 0.11s 13M

3.13 alpine (musl) - - 0.10s 12.2M

3.13 slim (glibc) - - 0.10s 13M

3.9 alpine (musl) - - 0.07s 18.2M

3.9 slim (glibc) - - 0.06s 19M

Imports

x509
```
from asn1crypto import x509
```
Ensure correct import path to access X.509 certificate parsing and serialization.

Quickstart stale last tested: 2026-04-23

A basic example demonstrating how to load, parse, and access details of an X.509 certificate using asn1crypto.

from asn1crypto import x509

# Load a certificate from a file
with open('certificate.pem', 'rb') as f:
    cert_data = f.read()

# Parse the certificate
cert = x509.Certificate.load(cert_data)

# Access certificate details
print(cert.subject.native)  # Print the subject of the certificate
print(cert.serial_number)   # Print the serial number of the certificate