program RijndaelTool;  { Copyright (c) 2001, Tom Verhoeff (TUE) }  { Version 1.0 (July 2001) }  { Interactive example program using FreePascal library RijndaelECB }uses RijndaelECB;procedure Pad0 ( var s: String );  begin    s := UpCase ( s )  ; while Length ( s ) < HexStrLen do begin      s := s + '0'    end { while }  end; { Pad0 }procedure Interact;  { interactively encrypt/decrypt messages }  const    Unmodified = '';             { to mark unmodified block }    Modified   = ' <-- updated'; { to mark modified block }  var    command: Char; { input command }    p, k, c, tmp: HexStr;    pt, ck, ct: Block;    pStatus, kStatus, cStatus: String;  begin    p := ''  ; k := ''  ; c := ''  ; pStatus := Unmodified  ; kStatus := Unmodified  ; cStatus := Unmodified  ; repeat      writeln    ; Pad0 ( p )    ; Pad0 ( k )    ; Pad0 ( c )    ; writeln ( 'Plaintext  = ', p, pStatus )    ; writeln ( 'Key        = ', k, kStatus )    ; writeln ( 'Ciphertext = ', c, cStatus )    ; writeln ( 'HexStr index 12345678901234567890123456789012 (mod 10)' )    ; writeln ( 'Block index   0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 (mod 10)' )    ; pStatus := Unmodified    ; kStatus := Unmodified    ; cStatus := Unmodified    ; write ( 'P(laintext, K(ey, C(iphertext, E(ncrypt, D(ecrypt, S(wap, Q(uit? ' )    ; readln ( command )    ; command := UpCase ( command )    ; case command of      'P': begin          write ( 'Plaintext?   ' )        ; readln ( p )        ; pStatus := Modified        end;      'K': begin          write ( 'Key?         ' )        ; readln ( k )        ; kStatus := Modified        end;      'C': begin          write ( 'Ciphertext?  ' )        ; readln ( c )        ; cStatus := Modified        end;      'E': begin          HexStrToBlock ( p, pt )        ; HexStrToBlock ( k, ck )        ; Encrypt ( pt, ck, ct )        ; BlockToHexStr ( ct, c )        ; writeln ( 'Encrypted plaintext with key to ciphertext' )        ; cStatus := Modified        end;      'D': begin          HexStrToBlock ( c, ct )        ; HexStrToBlock ( k, ck )        ; Decrypt ( ct, ck, pt )        ; BlockToHexStr ( pt, p )        ; writeln ( 'Decrypted ciphertext with key to plaintext' )        ; pStatus := Modified        end;      'S': begin          tmp := p        ; p := c        ; c := tmp        ; writeln ( 'Swapped plaintext and ciphertext' )        ; pStatus := Modified        ; cStatus := Modified        end;      'Q': writeln ( 'End of Interaction with RijndaelECB' );      else writeln ( 'Unknown command ''', command, '''' )      end { case }    until command = 'Q'  end; { Interact }begin  writeln ( 'Interactive Tool for Using FreePascal Library RijndaelECB' ); Interactend.