const a = '1234567890qwertyuiopasdfghjklzxcvbnmQWERTYUIOPASDFGHJKLZXCVBNM1234567890';

var Key: string;

function generateKey: string;
  var i: integer;
begin
  for i:=1 to 12 do Result:=Result+a[Random(62)];
end;

function encodeStr(str, key: string) : string;
  var i, i2: integer;
begin
  Result:='';
  for i:=1 to Length(str) do
  begin
    if i2 <= 12 then
    begin
      i2:=i2+1;
      Result:=Result + a[Pos(key[i2], a)];
      if i2 > 12 then i2:=1;
    end;
  end;
end;