C#

RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

See more Digital Signatures Examples

Signs a string to create a PKCS7 signature in the base64 encoding. The signature algorithm is RSASSA-PSS with SHA256. 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();

//  Get a digital certificate with private key from a .pfx
//  (Chilkat has many different ways to provide a cert + private key for siging.
//  Using a PFX is just one possible option.)
Chilkat.Pfx pfx = new Chilkat.Pfx();
success = pfx.LoadPfxFile("qa_data/rsassa-pss/privatekey.pfx","PFX_PASSWORD");
if (success == false) {
    Debug.WriteLine(pfx.LastErrorText);
    return;
}

//  Get the certificate to be used for signing.
//  (The typical case for a PFX is that it contains a cert with an associated private key,
//  as well as other certificates in the chain of authentication.  The cert with the private
//  key should be in the first position at index 0.)

Chilkat.Cert cert = new Chilkat.Cert();
success = pfx.CertAt(0,cert);
if (success == false) {
    Debug.WriteLine(pfx.LastErrorText);
    return;
}

crypt.SetSigningCert(cert);

//  Indicate that RSASSA-PSS with SHA256 should be used.
crypt.SigningAlg = "pss";
crypt.HashAlgorithm = "sha256";

crypt.EncodingMode = "base64";

//  Sign a string and return the base64 PKCS7 detached signature
string originalText = "This is a test";
string pkcs7sig = crypt.SignStringENC(originalText);
Debug.WriteLine("Detached Signature:");
Debug.WriteLine(pkcs7sig);

//  This signature looks like this:
//  MIIG5wYJKoZIhvcNAQcCoIIG2DCCBtQCAQExDzANBgl .. YToLqEwTdU87ox5g7rvw==

//  The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
//  then copy-and-paste the Base64 signature into the form and decode..

//  The signature can be verified against the original data like this:
success = crypt.VerifyStringENC(originalText,pkcs7sig);
Debug.WriteLine("Signature verified: " + Convert.ToString(success));
success = crypt.VerifyStringENC("Not the original text",pkcs7sig);
Debug.WriteLine("Signature verified: " + Convert.ToString(success));

//  Now we'll create an opaque signature (the opposite of a detached signature). 
//  An opaque signature is a PKCS7 message that contains both the original data and
//  the signature.  The verification process extracts the original data.
string opaqueSig = crypt.OpaqueSignStringENC(originalText);
Debug.WriteLine("Opaque Signature:");
Debug.WriteLine(opaqueSig);

//  The ASN.1 of the signature can be examined by browsing to https://lapo.it/asn1js/ ,
//  then copy-and-paste the Base64 signature into the form and decode..

//  We can verify and extract the original data:
string origTxt = crypt.OpaqueVerifyStringENC(opaqueSig);
if (crypt.LastMethodSuccess != true) {
    Debug.WriteLine("Signature verification failed.");
    Debug.WriteLine(crypt.LastErrorText);
    return;
}

Debug.WriteLine("Signature verified.");
Debug.WriteLine("Extracted text:" + origTxt);