Ever wanted to encrypt a text message?
In order to do that we need some helper functions like transforming the string to it's hex representation after encryption so we don't loose any characters plus it looks very good:

function StringToHexStr(const value: string): string;
begin
  SetLength(Result, Length(value) *2);
  if Length(value) > 0 then
    BinToHex(PChar(value), PChar(Result), Length(value));
end;

function HexStrToString(const value: string): string;
begin
  SetLength(Result, Length(value) div 2);
  if Length(value) > 0 then
    HexToBin(PChar(value), PChar(Result), Length(value));
end;

ok... now we need a hash function so we hash our password string

function hashKey(const Key: String): Integer;
var
  Index: Integer;
begin
  Result := 0;;
  for Index := 1 to Length(Key) do
    Result := ((Result shl 7) or (Result shr 25)) + Ord(Key[Index]);
end;

Note that you can use any hash functions you like as long as it's result type is Cardinal or Integer(unsigned long or signed long) this hash function is taken from (RemObjects Software) PascalScript's "uPSUtils.pas" unit, now we need the algorithm

function __encrypt(const Key, Source: String): String;
// this function should not be used directly
// use EncryptText and DecryptText
const
  szBuffer = SizeOf(Integer); (* 4 bytes *)
  szByteBuffer = SizeOf(Byte); (* 1 byte *)
var
  byteBuffer,
  buffer,
  index,
  theKey: Integer;
  StreamOut,
  StreamIn: TStringStream;
begin
  (* hash the key and store it on local integer variable *)
  theKey := hashKey(Key);
  (* create two TStringStream's:
     - one for the actual data
     - the other one for the encrypted/decrypted data *)
  StreamIn := TStringStream.Create(Source);
  StreamOut := TStringStream.Create('');
  (* make sure position is set to ZERO !! *)
  StreamIn.Position := 0;
  StreamOut.Position := 0;

  (* now loop WHILE number of bytes read is less than
     number of total bytes AND the difference between
     position and size is greater or equal to szBuffer
     which is 4 bytes *)
  while (StreamIn.Position < StreamIn.Size) and
    ((StreamIn.Size -StreamIn.Position) >= szBuffer) do begin
    (* read 4 bytes at a time into a local integer variable *)
    StreamIn.ReadBuffer(buffer, szBuffer);
    (* the XOR encryption/decryption *)
    buffer := buffer xor theKey;
    buffer := buffer xor $E0F;
    (* write data to output stream *)
    StreamOut.WriteBuffer(buffer, szBuffer);
  end;

  (* check if we have some bytes left, there's a fat
     chance we do... *)
  if (StreamIn.Size -StreamIn.Position) >= 1 then
    for index := StreamIn.Position to StreamIn.Size -1 do begin
      (* we should have 1, 2 or 3 bytes left MAX, so we
         read 1 byte at a time *)
      StreamIn.ReadBuffer(byteBuffer, szByteBuffer);
      (* the XOR encryption/decryption *)
      byteBuffer := byteBuffer xor $F;
      (* write data to output stream *)
      StreamOut.WriteBuffer(byteBuffer, szByteBuffer);
    end;

  (* set output stream's postion to ZERO so we can
     read it's data *)
  StreamOut.Position := 0;
  (* read data from output stream and return it's value *)
  Result := StreamOut.ReadString(StreamOut.Size);

  (* free allocated memory *)
  FreeAndNil(StreamIn);
  FreeAndNil(StreamOut);
end;

the encryption and decryption functions

(* this function should be used ONLY for encryption *)
function EncryptText(const Key, Source: String): String;
begin
  (* return the encrypted data *)
  Result := __encrypt(Key, Source);
  (* convert string to hex string *)
  Result := StringToHexStr(Result);
end;

(* this function should be used ONLY for decryption *)
function DecryptText(const Key, Source: String): String;
begin
  (* convert each hex string to string *)
  Result := HexStrToString(Source);
  (* return the decrypted data *)
  Result := __encrypt(Key, Result);
end;

Here's the encryption result of string "http://delphigeist.blogspot.com"

124CE8194017B30D1F54EC01135FF900094CB20B1657FB1A0A57E8476C6062