'How do I use a X509 certificate with PyCrypto?
I want to encrypt some data in python with PyCrypto.
However I get an error when using key = RSA.importKey(pubkey)
:
RSA key format is not supported
The key was generated with:
openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout mycert.key -out mycert.pem
The code is:
def encrypt(data):
pubkey = open('mycert.pem').read()
key = RSA.importKey(pubkey)
cipher = PKCS1_OAEP.new(key)
return cipher.encrypt(data)
Solution 1:[1]
PyCrypto does not support X.509 certificates. You must first extract the public key with the command:
openssl x509 -inform pem -in mycert.pem -pubkey -noout > publickey.pem
Then, you can use RSA.importKey
on publickey.pem
.
If you don't want or cannot use openssl, you can take the PEM X.509 certificate and do it in pure Python like this:
from Crypto.Util.asn1 import DerSequence
from Crypto.PublicKey import RSA
from binascii import a2b_base64
# Convert from PEM to DER
pem = open("mycert.pem").read()
lines = pem.replace(" ",'').split()
der = a2b_base64(''.join(lines[1:-1]))
# Extract subjectPublicKeyInfo field from X.509 certificate (see RFC3280)
cert = DerSequence()
cert.decode(der)
tbsCertificate = DerSequence()
tbsCertificate.decode(cert[0])
subjectPublicKeyInfo = tbsCertificate[6]
# Initialize RSA key
rsa_key = RSA.importKey(subjectPublicKeyInfo)
Solution 2:[2]
Here's a good example: https://www.dlitz.net/software/pycrypto/api/2.6/Crypto.Cipher.PKCS1_OAEP-module.html
from Crypto.Cipher import PKCS1_OAEP
from Crypto.PublicKey import RSA
# sender side
message = 'To be encrypted'
key = RSA.importKey(open('pubkey.der').read())
cipher = PKCS1_OAEP.new(key)
ciphertext = cipher.encrypt(message)
# receiver side
key = RSA.importKey(open('privkey.der').read())
cipher = PKCS1_OAEP.new(key)
message = cipher.decrypt(ciphertext)
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
Solution | Source |
---|---|
Solution 1 | |
Solution 2 | Kevin |