unit u_encrypt;//加密單元

interface

uses
classes;

const
C1:integer=12345;
C2:integer=54321;
//=================
g_pwdkey: Integer=888888;
function Encrypt(const S: string; Key: Word): string;
function Decrypt(const S: string; Key: Word): string;

implementation

function Encrypt(const S: string; Key: Word): string;//加密
var
  I: Integer;
begin
  Result := S;
  for I := 1 to Length(S) do
  begin
    Result[I] := char(byte(S[I]) xor (Key shr 13));
    Key := (byte(Result[I]) + Key) * C1 + C2;
  end;
  if Result='' then
    Result:='ERP';
end;

function Decrypt(const S: string; Key: Word): string;//解密
var
  I: Integer;
begin
  Result := S;
  if Result='ERP' then begin Result:=''; exit; end;
  for I := 1 to Length(S) do
  begin
    Result[I] := char(byte(S[I]) xor (Key shr 13));
    Key := (byte(S[I]) + Key) * C1 + C2;
  end;
end;

end.