(Delphi DLL) Streaming Encryption by Encrypting in Chunks

Encrypt data in chunks.

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, Crypt2, StringBuilder;

...

procedure TForm1.Button1Click(Sender: TObject);
var
crypt: HCkCrypt2;
txt1: PWideChar;
txt2: PWideChar;
txt3: PWideChar;
sbEncrypted: HCkStringBuilder;
i: Integer;
decryptedText: PWideChar;

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

crypt := CkCrypt2_Create();

CkCrypt2_putCryptAlgorithm(crypt,'aes');
CkCrypt2_putCipherMode(crypt,'cbc');
CkCrypt2_putKeyLength(crypt,128);

CkCrypt2_SetEncodedKey(crypt,'000102030405060708090A0B0C0D0E0F','hex');
CkCrypt2_SetEncodedIV(crypt,'000102030405060708090A0B0C0D0E0F','hex');

CkCrypt2_putEncodingMode(crypt,'hex');
txt1 := 'The quick brown fox jumped over the lazy dog.' + #13#10;
txt2 := '-' + #13#10;
txt3 := 'Done.' + #13#10;

sbEncrypted := CkStringBuilder_Create();

// Encrypt the 1st chunk:
// (don't worry about feeding the data to the encryptor in 
// exact multiples of the encryption algorithm's block size.
// Chilkat will buffer the data.)
CkCrypt2_putFirstChunk(crypt,True);
CkCrypt2_putLastChunk(crypt,False);
CkStringBuilder_Append(sbEncrypted,CkCrypt2__encryptStringENC(crypt,txt1));

// Encrypt the 2nd chunk
CkCrypt2_putFirstChunk(crypt,False);
CkCrypt2_putLastChunk(crypt,False);
CkStringBuilder_Append(sbEncrypted,CkCrypt2__encryptStringENC(crypt,txt2));

// Now encrypt N more chunks...
// Remember -- we're doing this in CBC mode, so each call
// to the encrypt method depends on the state from previous
// calls...
CkCrypt2_putFirstChunk(crypt,False);
CkCrypt2_putLastChunk(crypt,False);

for i := 0 to 4 do
  begin
    CkStringBuilder_Append(sbEncrypted,CkCrypt2__encryptStringENC(crypt,txt1));
    CkStringBuilder_Append(sbEncrypted,CkCrypt2__encryptStringENC(crypt,txt2));
  end;

// Now encrypt the last chunk:
CkCrypt2_putFirstChunk(crypt,False);
CkCrypt2_putLastChunk(crypt,True);
CkStringBuilder_Append(sbEncrypted,CkCrypt2__encryptStringENC(crypt,txt3));

Memo1.Lines.Add(CkStringBuilder__getAsString(sbEncrypted));

// Now decrypt in one call.
// (The data we're decrypting is both the first AND last chunk.)  
CkCrypt2_putFirstChunk(crypt,True);
CkCrypt2_putLastChunk(crypt,True);
decryptedText := CkCrypt2__decryptStringENC(crypt,CkStringBuilder__getAsString(sbEncrypted));

Memo1.Lines.Add(decryptedText);

// Note: You may decrypt in N chunks by setting the FirstChunk
// and LastChunk properties prior to calling the Decrypt* methods

CkCrypt2_Dispose(crypt);
CkStringBuilder_Dispose(sbEncrypted);

end;