Пример шифрования текста

const
  csCryptFirst = 20;
  csCryptSecond = 230;
  csCryptHeader = "Crypted";

type
  ECryptError = class(Exception);

function CryptString(Str:String):String;
var i,clen : Integer;
begin
  clen := Length(csCryptHeader);
  SetLength(Result, Length(Str)+clen);
  Move(csCryptHeader[1], Result[1], clen);
  For i := 1 to Length(Str) do
   begin
    if i mod 2 = 0 then
     Result[i+clen] := Chr(Ord(Str[i]) xor csCryptFirst)
    else
     Result[i+clen] := Chr(Ord(Str[i]) xor csCryptSecond);
   end;
end;

function UnCryptString(Str:String):String;
var i, clen : Integer;
begin
  clen := Length(csCryptHeader);
  SetLength(Result, Length(Str)-clen);
  if Copy(Str, 1, clen) < > csCryptHeader then
   raise ECryptError.Create("UnCryptString failed");

  For i := 1 to Length(Str)-clen do
   begin
    if (i) mod 2 = 0 then
     Result[i] := Chr(Ord(Str[i+clen]) xor csCryptFirst)
    else
     Result[i] := Chr(Ord(Str[i+clen]) xor csCryptSecond);
   end;
end;