C#

CMS Sign Hash

Demonstrates how to use the SignHashENC method to sign a pre-computed hash. This method creates a CMS signature (PKCS7 detached signature).

This example requires Chilkat v9.5.0.90 or later.

C#

bool success = false;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

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

// Create the hash to be signed...
crypt.HashAlgorithm = "sha256";
crypt.EncodingMode = "base64";
crypt.Charset = "utf-8";
// Create the SHA256 hash of a string using the utf-8 byte representation.
// Return the hash as base64.
string base64Hash = crypt.HashStringENC("This is the string to be hashed");

// Load a certificate for signing.
Chilkat.Cert cert = new Chilkat.Cert();
success = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123");
if (success == false) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

crypt.SetSigningCert(cert);

// Sign the hash to create a base64 CMS signature (which does not contain the original data).
// We can get the signature in a single line of base64 by specifying "base64", or 
// we can get multi-line base64 by specifying "base64_mime".
crypt.EncodingMode = "base64_mime";
string base64CmsSig = crypt.SignHashENC(base64Hash,"sha256","base64");
if (crypt.LastMethodSuccess == false) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

// Note: In the above call to SignHashENC, the encoding of the returned CMS signature is specified by the EncodingMode property.
// However, the encoding of the passed-in hash is indicated by the 3rd argument.

Debug.WriteLine("CMS Signature: " + base64CmsSig);