PKCS7 SignedData Detached Signature

How to create a PKCS7 detached signature. The resulting PKCS7 structure is encoded to a printable string using hex or base64 encoding. The data being signed is not included in the PKCS#7 structure.

Download Chilkat .NET for 2.0 / 3.5 Framework

Download Chilkat .NET for 1.0 / 1.1 Framework

Chilkat.Crypt2 crypt = new Chilkat.Crypt2();

//  Any string argument automatically begins the 30-day trial.
bool success;
success = crypt.UnlockComponent("30-day trial");
if (success != true) {
    MessageBox.Show("Crypt component unlock failed");
    return;
}

Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadByCommonName("Chilkat Software");
if (success != true) {
    MessageBox.Show(cert.LastErrorText);
    return;
}

//  Make sure this certificate has a private key available:
bool bHasPrivateKey;
bHasPrivateKey = cert.HasPrivateKey();
if (bHasPrivateKey != true) {
    MessageBox.Show("No private key available for signing.");
    return;
}

//  Tell the encryption component to use this cert.
crypt.SetSigningCert(cert);

string strData;
strData = "This is the data to be signed.";

//  Indicate that the PKCS7 signature should be returned
//  as a base64 encoded string:
crypt.EncodingMode = "base64";

//  The EncodingMode may be set to other values such as
//  "hex", "url", "quoted-printable", etc.

string strSignature;
strSignature = crypt.SignStringENC(strData);

textBox1.Text += strSignature + "\r\n";

//  Now verify the signature against the original data.

//  Tell the component what certificate to use for verification.
crypt.SetVerifyCert(cert);

success = crypt.VerifyStringENC(strData,strSignature);
if (success == true) {
    MessageBox.Show("digital signature verified");
}
else {
    MessageBox.Show("digital signature invalid");
}

//  Try it with incorrect data:
success = crypt.VerifyStringENC("This is not the signed data",strSignature);
if (success == true) {
    MessageBox.Show("digital signature verified");
}
else {
    MessageBox.Show("digital signature invalid");
}