Vigenere String Cesar algorithm Crypter

private
    { Déclarations privées }
      function Crypter:boolean;
      function Decrypter:boolean;
      function AlgoCesar(decalage:integer;texte:string):string;
      function VigenereCrypt(password,texte:string):string;
      function VigenereDecrypt(password,texte:string):string;
      
//

function Tform1.AlgoCesar(decalage:integer;texte:string):string;
var tmp:string;
    i:integer;
begin
  tmp:='';
  for i:=1 to length(texte) do
    begin
      tmp:=tmp+chr(ord(texte[i])+decalage);
    end;
  AlgoCesar:=tmp;
end;

function Tform1.VigenereCrypt(password,texte:string):string;
var i,nb:integer;
    tmp:string;
begin
  tmp:='';
  nb:=1;
  for i:=1 to length(texte) do
    begin
      tmp:=tmp+chr(ord(texte[i])+ord(password[nb]));
      nb:=nb+1;
      if nb>length(password) then
        begin
          nb:=1;
        end;
    end;
  VigenereCrypt:=tmp;
end;

function Tform1.VigenereDecrypt(password,texte:string):string;
var i,nb:integer;
    tmp:string;
begin
  tmp:='';
  nb:=1;
  for i:=1 to length(texte) do
    begin
      tmp:=tmp+chr((ord(texte[i])+256)-ord(password[nb]));
      nb:=nb+1;
      if nb>length(password) then
        begin
          nb:=1;
        end;
    end;
  VigenereDecrypt:=tmp;
end;

function Tform1.Crypter:boolean;
begin
     memo2.text:=VigenereCrypt(AlgoCesar(SpinEdit2.value,Edit1.text),
                               AlgoCesar((0-SpinEdit1.value),memo1.text));
     if AlgoCesar(SpinEdit1.value,
                  VigenereDeCrypt(AlgoCesar(SpinEdit2.value,edit1.text),Memo2.text))=Memo1.text then
      begin
        crypter:=true;
      end
      else
      begin
        crypter:=false;
      end;
end;

function Tform1.Decrypter:boolean;
begin
    Memo1.text := AlgoCesar(SpinEdit1.value,
            VigenereDeCrypt(AlgoCesar(SpinEdit2.value,edit1.text),memo2.text));
end;

Crypt :

procedure TForm1.Button1Click(Sender: TObject);
begin
  if crypter=true then
    begin
      //showmessage('Crypt done !');
    end
    else
    begin
      //showmessage('Crypt failed !');
    end;
end;

Decrypt :

procedure TForm1.Button2Click(Sender: TObject);
begin
    Memo1.text:=AlgoCesar(SpinEdit1.value,
            VigenereDeCrypt(AlgoCesar(SpinEdit2.value,edit1.text),Memo2.text));
end;