library AES;

{ Important note about DLL memory management: ShareMem must be the
  first unit in your library's USES clause AND your project's (select
  Project-View Source) USES clause if your DLL exports any procedures or
  functions that pass strings as parameters or function results. This
  applies to all strings passed to and from your DLL--even those that
  are nested in records and classes. ShareMem is the interface unit to
  the BORLNDMM.DLL shared memory manager, which must be deployed along
  with your DLL. To avoid using BORLNDMM.DLL, pass string information
  using PChar or ShortString parameters. }

uses
  SysUtils,
  Classes,
  ElAES,
  Math;
  
{$R *.res}

function AESDecryptStr(StrIn, AESKey: PChar): PChar; stdcall;
function HexToString(S: string): string;
var
	i: integer;

begin
  Result := '';

  // Go throught every single hexadecimal characters, and convert
  // them to ASCII characters...
  for i := 1 to Length( S ) do
  begin
    // Only process chunk of 2 digit Hexadecimal...
  	if ((i mod 2) = 1) then
	  	Result := Result + Chr( StrToInt( '0x' + Copy( S, i, 2 )));
  end;
end;
var
  Source: TStringStream;
  Dest: TStringStream;
  Size: integer;
  Key: TAESKey128;
begin
  // Convert hexadecimal to a strings before decrypting...
  Source := TStringStream.Create( HexToString( strIn ));
  Dest   := TStringStream.Create( '' );

  try
    // Start decryption...
    Size := Source.Size;
    Source.ReadBuffer(Size, SizeOf(Size));

    // Prepare key...
    FillChar(Key, SizeOf(Key), 0);
    Move(PChar(AESKey)^, Key, Min(SizeOf(Key), Length(AESKey)));

    // Decrypt now...
    DecryptAESStreamECB(Source, Source.Size - Source.Position, Key, Dest);

    // Display unencrypted text...
    //Result := StrNew(PChar(Dest.DataString));
    Result := PChar(Dest.DataString);
  finally
    Source.Free;
    Dest.Free;
  end;
end;

//------------------------------------------------------------------------------
function AESEncryptStr(StrIn, AESKey: PChar): PChar; stdcall;
function StringToHex(S: string): string;
var
	i: integer;

begin
  Result := '';

  // Go throught every single characters, and convert them
  // to hexadecimal...
	for i := 1 to Length( S ) do
  	Result := Result + IntToHex( Ord( S[i] ), 2 );
end;
var
  Source: TStringStream;
  Dest: TStringStream;
  Size: integer;
  Key: TAESKey128;
begin
  // Encryption
  Source := TStringStream.Create(strIn );
  Dest   := TStringStream.Create( '' );

  try
    // Save data to memory stream...
    Size := Source.Size;
    Dest.WriteBuffer( Size, SizeOf(Size) );

    // Prepare key...
    FillChar( Key, SizeOf(Key), 0 );
    Move( PChar(AESKey)^, Key, Min( SizeOf( Key ), Length( AESKey)));

    // Start encryption...
    EncryptAESStreamECB( Source, 0, Key, Dest );

    // Display encrypted text using hexadecimals...
    //Result := StrNew(PChar(StringToHex( Dest.DataString )));
    Result := PChar(StringToHex( Dest.DataString ));
  finally
    Source.Free;
    Dest.Free;
  end;
end;

exports
  AESDecryptStr, AESEncryptStr;

begin
  IsMultiThread := TRUE; 
end.