Tcl

Send an Email with a Digital Signature

Demonstrates the Chilkat Email.SendSigned property. Set it to true to have the email sent with a digital signature (the default is false). Signing also requires a certificate with access to its private key. This example loads that certificate (and its private key) from a PFX file with Cert.LoadPfxFile, supplies it via SetSigningCert, and enables signed sending.

Background: Signing is the mirror image of encrypting. To encrypt for a recipient you use their public certificate; to sign you use your own private key, and recipients verify with your public certificate. A signature does not hide the message — a signed email is still readable by anyone — but it proves who sent it and guarantees the content was not tampered with. A PFX (also called PKCS#12, .pfx or .p12) is a password-protected file that bundles a certificate together with its private key, making it a convenient single-file source for signing credentials.

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Tcl


load ./chilkat.dll

set success 0

#  Demonstrates the Email.SendSigned property with a full signing setup.  Set SendSigned
#  to true to have the email sent with a digital signature.  Signing requires a certificate
#  with access to its private key, which we load here from a PFX (.pfx / .p12) file.

set email [new_CkEmail]

CkEmail_put_Subject $email "Signed email"
CkEmail_put_Body $email "This message will be sent with a digital signature."
CkEmail_put_From $email "alice@example.com"
CkEmail_AddTo $email "Bob" "bob@example.com"

#  Load the signing certificate (including its private key) from a PFX file.
#  The 2nd argument is the PFX password.
set cert [new_CkCert]

set success [CkCert_LoadPfxFile $cert "qa_data/certs/signer.pfx" "pfx_password"]
if {$success == 0} then {
    puts [CkCert_lastErrorText $cert]
    delete_CkEmail $email
    delete_CkCert $cert
    exit
}

#  Provide the signing certificate.
set success [CkEmail_SetSigningCert $email $cert]
if {$success == 0} then {
    puts [CkEmail_lastErrorText $email]
    delete_CkEmail $email
    delete_CkCert $cert
    exit
}

#  Request that the email be sent with a digital signature.
CkEmail_put_SendSigned $email 1

puts "SendSigned = [CkEmail_get_SendSigned $email]"

#  Note: The path "qa_data/certs/signer.pfx" is a relative local filesystem path,
#  relative to the current working directory of the running application.

delete_CkEmail $email
delete_CkCert $cert