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. Delphi 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
success: Boolean;
privKey: HCkPrivateKey;
rsa: HCkRsa;
strData: PWideChar;
hexSig: PWideChar;
cert: HCkCert;
pubKey: HCkPublicKey;
rsa2: HCkRsa;

begin
success := False;

// 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 = False) then
  begin
    Memo1.Lines.Add(CkPrivateKey__lastErrorText(privKey));
    Exit;
  end;

rsa := CkRsa_Create();

// Import the private key into the RSA component:
success := CkRsa_UsePrivateKey(rsa,privKey);
if (success = False) 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 sha256 hash algorithm.
// Other valid choices are "md2", "sha1", "sha384",
// "sha512", and "md5".
hexSig := CkRsa__signStringENC(rsa,strData,'sha256');

Memo1.Lines.Add(hexSig);

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

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

pubKey := CkPublicKey_Create();
CkCert_GetPublicKey(cert,pubKey);

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

// Import the public key into the RSA object:
success := CkRsa_UsePublicKey(rsa2,pubKey);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

// 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,'sha256',hexSig);
if (success = False) then
  begin
    Memo1.Lines.Add(CkRsa__lastErrorText(rsa2));
    Exit;
  end;

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

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

end;