Chilkat2-Python

Add a Detached Signature with a Separate Private Key

Demonstrates the Chilkat Mime.AddDetachedSignaturePk method, which creates a detached signature using a signer certificate and its separately supplied private key. The first argument is the Cert and the second is the PrivateKey.

Note: The file paths are relative to the application's current working directory. Absolute paths may also be used. Supply the paths appropriate to your own environment.

Background: Sometimes the certificate and its private key live apart — a .cer alongside a PEM key file, for instance — rather than bundled in a single PFX. This method pairs them explicitly for signing, whereas AddDetachedSignature expects a Cert that already provides its key. The result is the same multipart/signed message.

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import sys
import chilkat2

success = False

mime = chilkat2.Mime()
success = mime.SetBodyFromPlainText("This message will be signed.")
if (success == False):
    print(mime.LastErrorText)
    sys.exit()

# Load the certificate and its private key separately.
cert = chilkat2.Cert()
success = cert.LoadFromFile("qa_data/signer.cer")
if (success == False):
    print(cert.LastErrorText)
    sys.exit()

privKey = chilkat2.PrivateKey()
success = privKey.LoadPemFile("qa_data/signer_privkey.pem")
if (success == False):
    print(privKey.LastErrorText)
    sys.exit()

# Create a detached signature when the certificate and private key are supplied separately.  The
# 1st argument is the signer certificate and the 2nd is its private key.
success = mime.AddDetachedSignaturePk(cert,privKey)
if (success == False):
    print(mime.LastErrorText)
    sys.exit()

success = mime.SaveMime("qa_output/signed.eml")
if (success == False):
    print(mime.LastErrorText)
    sys.exit()

print("Detached signature added.")