CkPython

CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

CkPython

import sys
import chilkat

success = False

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

crypt = chilkat.CkCrypt2()

# Create the hash to be signed...
crypt.put_HashAlgorithm("sha256")
crypt.put_EncodingMode("base64")
crypt.put_Charset("utf-8")
# Create the SHA256 hash of a string using the utf-8 byte representation.
# Return the hash as base64.
base64Hash = crypt.hashStringENC("This is the string to be hashed")

# Load a certificate for signing.
cert = chilkat.CkCert()
success = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123")
if (success == False):
    print(cert.lastErrorText())
    sys.exit()

crypt.SetSigningCert(cert)

# Sign the hash to create a base64 CMS signature (which does not contain the original data).
# We can get the signature in a single line of base64 by specifying "base64", or 
# we can get multi-line base64 by specifying "base64_mime".
crypt.put_EncodingMode("base64_mime")
base64CmsSig = crypt.signHashENC(base64Hash,"sha256","base64")
if (crypt.get_LastMethodSuccess() == False):
    print(crypt.lastErrorText())
    sys.exit()

# Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
# However, the encoding of the passed-in hash is indicated by the 3rd argument.

print("CMS Signature: " + base64CmsSig)