(Python) Encrypt File using X.509 Certificate using AES in CBC Mode

Demonstrates how to encrypt a file using an X.509 Certificate's public key, where the underlying bulk encryption algorithm is 128-bit AES in CBC mode. (The underlying bulk encryption algorithm can be specified to be other algorithms/strengths.)

Chilkat Python Downloads install with pip pip3 install chilkat or download... Python Module for Windows, MacOS, Linux, Alpine Linux, Solaris

import sys
import chilkat

#  This example requires the Chilkat Crypt API to have been previously unlocked.
#  See Unlock Chilkat Crypt for sample code.

crypt = chilkat.CkCrypt2()

#  Use public-key cryptography for encryption.
crypt.put_CryptAlgorithm("pki")

#  Get an X.509 certificate to use for encrypting.
#  Note: Chilkat provides many different ways of loading a certificate, from many different formats,
#  or if on Windows, from the installed certificates on the system.
#  This example simply loads a certificate from a file.
#  Also, for encryption, only the public key is needed.  Digital certificates embed the public key
#  within the X.509 format itself.  Therefore, if you have a certificate, you also have the public key.
cert = chilkat.CkCert()
success = cert.LoadFromFile("qa_data/certs/testCert.cer")
if (success != True):
    print(cert.lastErrorText())
    sys.exit()

success = crypt.SetEncryptCert(cert)
if (success != True):
    print(crypt.lastErrorText())
    sys.exit()

#  Indicate the underlying bulk encryption algorithm to be used:
crypt.put_Pkcs7CryptAlg("aes")
crypt.put_KeyLength(128)

#  Note: When doing public-key encryption the underlying bulk symmetric cipher mode will always be CBC. (at least with Chilkat...)

#  There's one last option that could be set.  If is the RSA encryption encryption/padding scheme.
#  By default, RSAES_PKCS1-V1_5 is used.  If desired, the OaepPadding property could be set to True to
#  use RSAES_OAEP.  (We'll leave it set at the default value of False)
crypt.put_OaepPadding(False)

#  Everything is specified.  Now just encrypt...
#  The output is PKCS7 in binary DER format.
success = crypt.CkEncryptFile("qa_data/hamlet.xml","qa_output/hamlet.p7")
if (success != True):
    print(crypt.lastErrorText())
    sys.exit()

print("Finished.")