(Delphi DLL) Encrypt a file to a PKCS7 encrypted message using multiple certificates from different users

Demonstrates how to encrypt a file to a PKCS7 encrypted message using multiple certificates from different users. Any one of the users can decrypt using his/her own certificate + private key.

Note: When doing public key encryption, it is the public key that is used to encrypt. The private key is required for decryption.

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, BinData, Cert, Crypt2;

...

procedure TForm1.Button1Click(Sender: TObject);
var
crypt: HCkCrypt2;
cert1: HCkCert;
success: Boolean;
cert2: HCkCert;
cert3: HCkCert;
fileData: HCkBinData;

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

crypt := CkCrypt2_Create();

//  Tell the crypt object to use 3 certificates.
//  Do this by calling AddEncryptCert for each certificate.

//  Load a digital certificate.
//  We don't need the private key for encryption.
//  Only the public key is needed (which is included in a certificate).
cert1 := CkCert_Create();
success := CkCert_LoadFromFile(cert1,'qa_data/user1/cert_user1.pem');
//  Assume success for the example, but make sure your application checks for success/failure...
CkCrypt2_AddEncryptCert(crypt,cert1);

cert2 := CkCert_Create();
success := CkCert_LoadFromFile(cert2,'qa_data/user2/cert_user2.pem');
CkCrypt2_AddEncryptCert(crypt,cert2);

cert3 := CkCert_Create();
success := CkCert_LoadFromFile(cert3,'qa_data/user3/cert_user3.pem');
CkCrypt2_AddEncryptCert(crypt,cert3);

//  Indicate that we want PKI encryption (i.e. public-key infrastructure)
//  to produce a CMS message (Cryptographic Message Syntax/PKCS7),
//  that is be created with RSAES-OAEP padding, SHA256, and AES-128 for the
//  bulk encryption.
CkCrypt2_putCryptAlgorithm(crypt,'pki');
CkCrypt2_putPkcs7CryptAlg(crypt,'aes');
CkCrypt2_putKeyLength(crypt,128);
CkCrypt2_putOaepHash(crypt,'sha256');
CkCrypt2_putOaepPadding(crypt,True);

//  Load the file to be encrypted...
fileData := CkBinData_Create();
success := CkBinData_LoadFile(fileData,'qa_data/jpg/penguins.jpg');
//  Your app should check for success/failure..

//  Encrypt the data.  The contents of the fileData object are replaced with the PKCS7 encrypted message.
success := CkCrypt2_EncryptBd(crypt,fileData);
if (success <> True) then
  begin
    Memo1.Lines.Add(CkCrypt2__lastErrorText(crypt));
    Exit;
  end;

//  Save the PKCS7 encrypted message to a file..
success := CkBinData_WriteFile(fileData,'qa_output/pkcs7_encrypted.p7');

//  Now indicate that the PKCS7 output is to be returned in the base64 encoding.
CkCrypt2_putEncodingMode(crypt,'base64');

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

CkCrypt2_Dispose(crypt);
CkCert_Dispose(cert1);
CkCert_Dispose(cert2);
CkCert_Dispose(cert3);
CkBinData_Dispose(fileData);

end;