(C#) Sign JSON (or any Text) to Create a Detached PKCS7 Signature

Demonstrates how to sign JSON or any string using a certificate + private key from a .p12/.pfx to create a detached PKCS7 signature. (A detached signature is one that does not embed the original signed data.)

Chilkat .NET Downloads Chilkat .NET Framework Chilkat for .NET Core

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

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

Chilkat.Cert cert = new Chilkat.Cert();
bool success = cert.LoadPfxFile("qa_data/pfx/cert_test123.pfx","test123");
if (success != true) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

// Tell the crypt component to use this cert.
success = crypt.SetSigningCert(cert);
if (success != true) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

crypt.HashAlgorithm = "sha256";

// By default, all the certs in the chain of authentication are included in the signature.
// If desired, we can choose to only include the signing certificate:
crypt.IncludeCertChain = false;

// Create the detached signature, which does NOT contain the original data.
// To create a PKCS7 signature that contains the original data, see CAdES Sign JSON
crypt.Charset = "utf-8";
byte[] detachedSig = null;
string stringToSign = "{ \"abc\": 123}";
detachedSig = crypt.SignString(stringToSign);
if (crypt.LastMethodSuccess == false) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

// Verify the signature against the original data.
bool verified = crypt.VerifyString(stringToSign,detachedSig);
if (verified == false) {
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

Debug.WriteLine("Success!");