(Delphi DLL) RSA Signature/Verify with .key and .cer

See more RSA Examples

Demonstrates how to use a .key file (private key) and digital certificate (.cer, public key) to create and verify an RSA signature.

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, PublicKey, PrivateKey, Rsa, Cert;

...

procedure TForm1.Button1Click(Sender: TObject);
var
privKey: HCkPrivateKey;
success: Boolean;
privKeyXml: PWideChar;
rsa: HCkRsa;
strData: PWideChar;
hexSig: PWideChar;
cert: HCkCert;
pubKey: HCkPublicKey;
rsa2: HCkRsa;

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

privKey := CkPrivateKey_Create();

// Load the private key from an RSA .key file:
success := CkPrivateKey_LoadPemFile(privKey,'privateKey.key');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

// Get the private key in XML format:
privKeyXml := CkPrivateKey__getXml(privKey);

rsa := CkRsa_Create();

// Import the private key into the RSA component:
success := CkRsa_ImportPrivateKey(rsa,privKeyXml);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa));
    Exit;
  end;

// Create the signature as a hex string:
CkRsa_putEncodingMode(rsa,'hex');

strData := 'This is the string to be signed.';

// Sign the string using the sha-1 hash algorithm.
// Other valid choices are "md2", "sha256", "sha384",
// "sha512", and "md5".
hexSig := CkRsa__signStringENC(rsa,strData,'sha-1');

Memo1.Lines.Add(hexSig);

// Load a digital certificate from a .cer file:
cert := CkCert_Create();

success := CkCert_LoadFromFile(cert,'myCert.cer');
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCert__lastErrorText(cert));
    Exit;
  end;

pubKey := CkCert_ExportPublicKey(cert);

// Now verify using a separate instance of the RSA object:
rsa2 := CkRsa_Create();

// Import the public key into the RSA object:
success := CkRsa_ImportPublicKey(rsa2,CkPublicKey__getXml(pubKey));
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

CkPublicKey_Dispose(pubKey);

// The signature is a hex string, so make sure the EncodingMode is correct:
CkRsa_putEncodingMode(rsa2,'hex');

// Verify the signature:
success := CkRsa_VerifyStringENC(rsa2,strData,'sha-1',hexSig);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

Memo1.Lines.Add('Success.');

CkPrivateKey_Dispose(privKey);
CkRsa_Dispose(rsa);
CkCert_Dispose(cert);
CkRsa_Dispose(rsa2);

end;