(Delphi ActiveX) Encrypt File in Chunks using AES CBC

Demonstrates how to use the FirstChunk/LastChunk properties to encrypt a file chunk-by-chunk.

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

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
crypt: TChilkatCrypt2;
fileToEncrypt: WideString;
facIn: TCkFileAccess;
success: Integer;
outputEncryptedFile: WideString;
facOutEnc: TCkFileAccess;
chunkSize: Integer;
numChunks: Integer;
bd: TChilkatBinData;
i: Integer;
decryptedFile: WideString;
bSame: Integer;

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

crypt := TChilkatCrypt2.Create(Self);

crypt.CryptAlgorithm := 'aes';
crypt.CipherMode := 'cbc';
crypt.KeyLength := 128;

crypt.SetEncodedKey('000102030405060708090A0B0C0D0E0F','hex');
crypt.SetEncodedIV('000102030405060708090A0B0C0D0E0F','hex');

fileToEncrypt := 'qa_data/hamlet.xml';
facIn := TCkFileAccess.Create(Self);
success := facIn.OpenForRead(fileToEncrypt);
if (success <> 1) then
  begin
    Memo1.Lines.Add('Failed to open file that is to be encrytped.');
    Exit;
  end;

outputEncryptedFile := 'qa_output/hamlet.enc';
facOutEnc := TCkFileAccess.Create(Self);
success := facOutEnc.OpenForWrite(outputEncryptedFile);
if (success <> 1) then
  begin
    Memo1.Lines.Add('Failed to encrypted output file.');
    Exit;
  end;

// Let's encrypt in 10000 byte chunks.
chunkSize := 10000;
numChunks := facIn.GetNumBlocks(chunkSize);

crypt.FirstChunk := 1;
crypt.LastChunk := 0;

bd := TChilkatBinData.Create(Self);

i := 0;
while i < numChunks do
  begin
    i := i + 1;
    if (i = numChunks) then
      begin
        crypt.LastChunk := 1;
      end;

    // Read the next chunk from the file.
    // The last chunk will be whatever amount remains in the file..
    bd.Clear();
    facIn.FileReadBd(chunkSize,bd.ControlInterface);

    // Encrypt.
    crypt.EncryptBd(bd.ControlInterface);

    // Write the encrypted chunk to the output file.
    facOutEnc.FileWriteBd(bd.ControlInterface,0,0);

    crypt.FirstChunk := 0;
  end;

// Make sure both FirstChunk and LastChunk are restored to 1 after
// encrypting or decrypting in chunks.  Otherwise subsequent encryptions/decryptions
// will produce unexpected results.
crypt.FirstChunk := 1;
crypt.LastChunk := 1;

facIn.FileClose();
facOutEnc.FileClose();

// Decrypt the encrypted output file in a single call using CBC mode:
decryptedFile := 'qa_output/hamlet_dec.xml';
success := crypt.CkDecryptFile(outputEncryptedFile,decryptedFile);
// Assume success for the example..

// Compare the contents of the decrypted file with the original file:
bSame := facIn.FileContentsEqual(fileToEncrypt,decryptedFile);
Memo1.Lines.Add('bSame = ' + IntToStr(Ord(bSame)));
end;