delphi EncryptIt.pas

unit EncryptIt; 
 
interface 
USES 
    Classes; 
const 
     C1 = 52845; 
     C2 = 22719; 
 
function Encrypt(const S: String; Key: Word): String; 
function Decrypt(const S: String; Key: Word): String; 
procedure EncryptFile(INFName, OutFName : String; Key : Word); 
procedure DecryptFile(INFName, OutFName : String; Key : Word); 
 
implementation 
 
function Encrypt(const S: String; Key: Word): String; 
var 
   I: Integer; 
begin 
  Result := S; 
  for I := 1 to Length(S) do 
      begin 
           Result[I] := char(byte(S[I]) xor (Key shr 8)); 
           Key := (byte(Result[I]) + Key) * C1 + C2; 
      end; 
  end; 
 
function Decrypt(const S: String; Key: Word): String; 
var 
   I: Integer; 
begin 
  Result := S; 
  for I := 1 to Length(S) do 
      begin 
           Result[I] := char(byte(S[I]) xor (Key shr 8)); 
           Key := (byte(S[I]) + Key) * C1 + C2; 
      end; 
  end; 
 
 
procedure EncryptFile(INFName, OutFName : String; Key : Word); 
VAR 
   MS, SS : TMemoryStream; 
   X : Integer; 
   C : Byte; 
begin 
MS := TMemoryStream.Create; 
SS := TMemoryStream.Create; 
    TRY 
       MS.LoadFromFile(INFName); 
       MS.Position := 0; 
       FOR X := 0 TO MS.Size - 1 DO 
             begin 
                  MS.Read(C, 1); 
                  C := (C xor (Key shr 8)); 
                  Key := (C + Key) * C1 + C2; 
                  SS.Write(C,1); 
             end; 
       SS.SaveToFile(OutFName); 
    FINALLY 
           SS.Free; 
           MS.Free; 
    end; 
end; 
 
procedure DecryptFile(INFName, OutFName : String; Key : Word); 
VAR 
   MS, SS : TMemoryStream; 
   X : Integer; 
   C, O : Byte; 
begin 
MS := TMemoryStream.Create; 
SS := TMemoryStream.Create; 
    TRY 
       MS.LoadFromFile(INFName); 
       MS.Position := 0; 
       FOR X := 0 TO MS.Size - 1 DO 
             begin 
                  MS.Read(C, 1); 
                  O := C; 
                  C := (C xor (Key shr 8)); 
                  Key := (O + Key) * C1 + C2; 
                  SS.Write(C,1); 
             end; 
       SS.SaveToFile(OutFName); 
    FINALLY 
           SS.Free; 
           MS.Free; 
    end; 
end; 
 
end.