(Chilkat2-Python) A3/A4 Certificate to Create and Verify an Opaque PKCS7/CMS Signature

Demonstrates how to use an A3 or A4 certificate w/ private key on a smartcard or token 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.

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import sys
import chilkat2

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

crypt = chilkat2.Crypt2()

# 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 smartcards and hardware tokens, PFX/.p12, Java keystore, JWK, Windows registry-based certificate stores, and other sources.
# This example will load the default certificate from the smartcard that is currently in
# the smartcard reader.

cert = chilkat2.Cert()

# If the smartcard or token requires a PIN, we can set it here to avoid the dialog...
cert.SmartCardPin = "000000"

success = cert.LoadFromSmartcard("")
if (success != True):
    print(cert.LastErrorText)
    sys.exit()

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

# Indicate we want the opaque signature in base64 format:
crypt.EncodingMode = "base64"

# Sign the string using the "utf-8" byte representation:
crypt.Charset = "utf-8"

# Create the opaque signature:
originalData = "This is the string to be signed."
opaqueSig = crypt.OpaqueSignStringENC(originalData)
if (crypt.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 = chilkat2.Crypt2()

# We only need the certificate to verify a signature (and extract the data from
# an opaque signature).  The public key is always embedded within a certificate.
success = vCrypt.SetVerifyCert(cert)
if (success != True):
    print(vCrypt.LastErrorText)
    sys.exit()

vCrypt.EncodingMode = "base64"
vCrypt.Charset = "utf-8"

extractedData = vCrypt.OpaqueVerifyStringENC(opaqueSig)
if (vCrypt.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.