Objective-C

Check if a MIME Entity is Signed (S/MIME)

Demonstrates the Chilkat Mime.IsSigned method, which returns whether the entity is a complete CMS/PKCS #7 signed S/MIME wrapper, including detached multipart/signed and opaque forms. It takes no arguments.

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

Background: Before verifying a signature you need to know one is present, and this is the check. A signed S/MIME message comes in two shapes — detached (multipart/signed, signature alongside the content) and opaque (application/pkcs7-mime, content wrapped inside the signature) — and this recognizes both. Follow a true result with Verify.

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Objective-C

#import <CkoMime.h>

BOOL success = NO;

//  Demonstrates the Mime.IsSigned method, which returns whether the entity is a complete CMS/PKCS #7 signed S/MIME wrapper.  It takes no arguments.

CkoMime *mime = [[CkoMime alloc] init];
success = [mime LoadMimeFile: @"qa_data/signed.eml"];
if (success == NO) {
    NSLog(@"%@",mime.LastErrorText);
    return;
}

if ([mime IsSigned]) {
    NSLog(@"%@",@"This is a signed S/MIME message.");
}
else {
    NSLog(@"%@",@"This is not a signed S/MIME message.");
}