PKCS7 SignedData Signature (embeds Signed Data)

How to create a PKCS7 signature. The resulting PKCS7 structure is encoded to a printable string using hex or base64 encoding. The data being signed is embedded within the PKCS#7 structure.

Demonstrates how to verify the signature and recover the original data.

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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 strSignatureWithData;
strSignatureWithData = crypt.OpaqueSignStringENC(strData);

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

//  Now verify the signature against the original data.

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

string originalData;
originalData = crypt.OpaqueVerifyStringENC(strSignatureWithData);
if (originalData == null ) {
    //  The signature verification failed.
    MessageBox.Show(crypt.LastErrorText);
}
else {
    textBox1.Text += originalData + "\r\n";
    MessageBox.Show("Signature verified!");
}