(Delphi DLL) RSASSA-PSS Sign String to Create Base64 PCKS7 Signature

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

Note: This example requires Chilkat v9.5.0.67 or greater.

Chilkat for Delphi Downloads Chilkat non-ActiveX DLL for Delphi Chilkat ActiveX DLL for Delphi * The examples here use the non-ActiveX DLL.

uses
    Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
    Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Pfx, Cert, Crypt2;

...

procedure TForm1.Button1Click(Sender: TObject);
var
crypt: HCkCrypt2;
pfx: HCkPfx;
success: Boolean;
cert: HCkCert;
originalText: PWideChar;
pkcs7sig: PWideChar;
opaqueSig: PWideChar;
origTxt: PWideChar;

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

crypt := CkCrypt2_Create();

// 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.)
pfx := CkPfx_Create();
success := CkPfx_LoadPfxFile(pfx,'qa_data/rsassa-pss/privatekey.pfx','PFX_PASSWORD');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPfx__lastErrorText(pfx));
    Exit;
  end;

// 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.)
cert := CkPfx_GetCert(pfx,0);
if (CkPfx_getLastMethodSuccess(pfx) <> True) then
  begin
    Memo1.Lines.Add(CkPfx__lastErrorText(pfx));
    Exit;
  end;
CkCrypt2_SetSigningCert(crypt,cert);

// Indicate that RSASSA-PSS with SHA256 should be used.
CkCrypt2_putSigningAlg(crypt,'pss');
CkCrypt2_putHashAlgorithm(crypt,'sha256');

CkCrypt2_putEncodingMode(crypt,'base64');

// Sign a string and return the base64 PKCS7 detached signature
originalText := 'This is a test';
pkcs7sig := CkCrypt2__signStringENC(crypt,originalText);
Memo1.Lines.Add('Detached Signature:');
Memo1.Lines.Add(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 := CkCrypt2_VerifyStringENC(crypt,originalText,pkcs7sig);
Memo1.Lines.Add('Signature verified: ' + IntToStr(Ord(success)));
success := CkCrypt2_VerifyStringENC(crypt,'Not the original text',pkcs7sig);
Memo1.Lines.Add('Signature verified: ' + IntToStr(Ord(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.
opaqueSig := CkCrypt2__opaqueSignStringENC(crypt,originalText);
Memo1.Lines.Add('Opaque Signature:');
Memo1.Lines.Add(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:
origTxt := CkCrypt2__opaqueVerifyStringENC(crypt,opaqueSig);
if (CkCrypt2_getLastMethodSuccess(crypt) <> True) then
  begin
    Memo1.Lines.Add('Signature verification failed.');
    Memo1.Lines.Add(CkCrypt2__lastErrorText(crypt));
    CkCert_Dispose(cert);
    Exit;
  end;

Memo1.Lines.Add('Signature verified.');
Memo1.Lines.Add('Extracted text:' + origTxt);

CkCert_Dispose(cert);

CkCrypt2_Dispose(crypt);
CkPfx_Dispose(pfx);

end;