(CkPython) Create and Verify an Opaque PKCS7/CMS Signature

Demonstrates how to create a PKCS7 opaque signature, and also how to verify an opaque signature. An opaque signature is different than a detached PKCS7 signature in that it contains the original data. Verifying an opaque signature retrieves the original content.

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 assumes the Chilkat API to have been previously unlocked.
# See Global Unlock Sample for sample code.

crypt = chilkat.CkCrypt2()

# A certificate and private key is needed to create a signature.
# Chilkat provides many different ways to load a certificate and private key, such
# as from a PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
# This example will load the certificate from a .crt and the private key from a .key file

cert = chilkat.CkCert()
# The LoadFromFile method will automatically detect the format and load it.
success = cert.LoadFromFile("qa_data/certs/test_12345678a.cer")
if (success != True):
    print(cert.lastErrorText())
    sys.exit()

# Our private key is in an encrypted PKCS8 format.
# If you don't know the format of your key, but you do know it's encrypted,
# and requires a password, then just call any of the Chilkat methods that load
# a private key w/ a password argument.  Chilkat will auto-detect the format
# and load it correctly even if it's not the format indicated by the method name..
privKey = chilkat.CkPrivateKey()
password = "12345678a"
success = privKey.LoadPkcs8EncryptedFile("qa_data/certs/test_12345678a.key",password)
if (success != True):
    print(privKey.lastErrorText())
    sys.exit()

# Set properties required for signing.

# Tell it to use the cert and private key we've loaded.
success = crypt.SetSigningCert2(cert,privKey)
if (success != True):
    print(crypt.lastErrorText())
    sys.exit()

# Indicate we want the opaque signature in base64 format:
crypt.put_EncodingMode("base64")

# Sign the string using the "utf-8" byte representation:
crypt.put_Charset("utf-8")

# Create the opaque signature:
originalData = "This is the string to be signed."
opaqueSig = crypt.opaqueSignStringENC(originalData)
if (crypt.get_LastMethodSuccess() != True):
    print(crypt.lastErrorText())
    sys.exit()

print(opaqueSig)

# The output looks like this:
# MIIPgQYJKoZIhvcNAQcCoIIPcjCCD24CAQExCzAJBgUrDgMCGgUAMC8GCSqGSIb3DQEHAaAiBCBUaGlzIGlzIHRoZSBzdHJpbmcgdG8gYmUgc...

# ----------------------------------------------------------------------------------------------
# Now let's verify the signature and retrieve the original data.
# We'll use a new Crypt2 object to keep things completely separate...

vCrypt = chilkat.CkCrypt2()

vCrypt.put_EncodingMode("base64")
vCrypt.put_Charset("utf-8")

extractedData = vCrypt.opaqueVerifyStringENC(opaqueSig)
if (vCrypt.get_LastMethodSuccess() != True):
    print(vCrypt.lastErrorText())
    sys.exit()

print("The extracted data: " + extractedData)

# The output is:
# The extracted data: This is the string to be signed.