Objective-C

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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Objective-C

#import <CkoEmail.h>
#import <CkoCert.h>

BOOL success = NO;

//  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.

CkoEmail *email = [[CkoEmail alloc] init];
email.Subject = @"Signed email";
email.Body = @"This message will be sent with a digital signature.";
email.From = @"alice@example.com";
[email AddTo: @"Bob" emailAddress: @"bob@example.com"];

//  Load the signing certificate (including its private key) from a PFX file.
//  The 2nd argument is the PFX password.
CkoCert *cert = [[CkoCert alloc] init];
success = [cert LoadPfxFile: @"qa_data/certs/signer.pfx" password: @"pfx_password"];
if (success == NO) {
    NSLog(@"%@",cert.LastErrorText);
    return true;
}

//  Provide the signing certificate.
success = [email SetSigningCert: cert];
if (success == NO) {
    NSLog(@"%@",email.LastErrorText);
    return true;
}

//  Request that the email be sent with a digital signature.
email.SendSigned = YES;

NSLog(@"%@%d",@"SendSigned = ",email.SendSigned);

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