Delphi ActiveX

Duplicate openssl pkey -in private.pem -pubout -out pubkey.pem

See more OpenSSL Examples

How to output the public part of a private key: Demonstrates how to duplicate this OpenSSL command:

openssl pkey -in private.pem -pubout -out pubkey.pem

Delphi ActiveX

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

...

procedure TForm1.Button1Click(Sender: TObject);
var
success: Integer;
pkey: TPrivateKey;
pubKey: TPublicKey;

begin
success := 0;

pkey := TPrivateKey.Create(Self);

// Load the private key from an PEM file:
success := pkey.LoadPemFile('private.pem');
if (success = 0) then
  begin
    Memo1.Lines.Add(pkey.LastErrorText);
    Exit;
  end;

pubKey := TPublicKey.Create(Self);
pkey.ToPublicKey(pubKey.ControlInterface);

success := pubKey.SavePemFile(0,'pubKey.pem');
if (success <> 1) then
  begin
    Memo1.Lines.Add(pubKey.LastErrorText);

    Exit;
  end;

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