Text Encryption Unit

Publicado por luchin On viernes, 28 de enero de 2011 0 comentarios

Source Code

  1. unit unRC4;
  3. interface
  5. type
  6.   PByteArray = ^TByteArray;
  7.   TByteArray = Array [0..32767] Of Byte;
  9.   TRC4 = class
  10.   private
  11.     D               : array[Byte] of Byte;
  12.     I,J             : Byte;
  13.     procedure Init(const Key: string);
  14.     procedure Done;
  15.     procedure Code(Source, Dest: pChar; Count: Integer);
  16.   public
  17.     function Encrypt(S: pChar; const Password: string): AnsiString;
  18.     function Decrypt(S: pChar; const Password: string): AnsiString;
  19.   end;
  21. implementation
  23. { TRC4.Encrypt
  24.   This function will return the text(S) encrypted with the chosen password. }
  25. function TRC4.Encrypt(S: pChar; const Password: string): AnsiString;
  26. begin
  27.   SetLength(Result, Length(S));
  28.   Init(Password);
  29.   Code(pChar(S), pChar(Result), Length(S));
  30.   Done;
  31. end;
  33. { TRC4.Decrypt
  34.   This function will return the text(S) decrypted with the chosen password. }
  35. function TRC4.Decrypt(S: pChar; const Password: string): AnsiString;
  36. begin
  37.   SetLength(Result, Length(S));
  38.   Init(Password);
  39.   Code(pChar(S), pChar(Result), Length(S));
  40.   Done;
  41. end;
  43. { TRC4.Init
  44.   This routine will prepare the encryption/decryption. }
  45. procedure TRC4.Init(const Key: string);
  46. var
  47.   R, S, T, K        : Byte;
  48.   U,L               : Integer;
  49.   DummyArray        : array [0..1599] of Char;
  50. begin
  51. {$R-}
  52. {$Q-}
  53.   L := Length(Key);
  54.   I := 0;
  55.   J := 0;
  56.   R := 0;
  57.   U := 0;
  58.   for S := 0 to 255 do
  59.     D[S] := S;
  60.   for S := 0 to 255 do
  61.   begin
  62.     if (U < L) then
  63.       K := PByteArray(Key)[u]
  64.     else
  65.       K := 0;
  66.     Inc(U);
  67.     if (U >= L) then
  68.       U := 0;
  69.     Inc(R, D[S] + K);
  70.     T    := D[S];
  71.     D[S] := D[R];
  72.     D[R] := T;
  73.   end;
  74.   Code(@DummyArray, @DummyArray, 1600);
  75. end;
  77. { TRC4.Done
  78.   This routine will clean the variables used when encrypting/decrypting. }
  79. procedure TRC4.Done;
  80. begin
  81.   FillChar(D, sizeOf(D), 0);
  82.   FillChar(I, sizeOf(I), 0);
  83.   FillChar(J, sizeOf(J), 0);
  84. end;
  86. { TRC4.Code
  87.   This routine will encrypt the text. }
  88. procedure TRC4.Code(Source, Dest: pChar; Count: Integer);
  89. var
  90.   S                 : Integer;
  91.   T                 : Byte;
  92. begin
  93.   for S := 0 to (Count - 1) do
  94.   begin
  95.     Inc(I);
  96.     T := D[i];
  97.     Inc(J, T);
  98.     D[i] := D[J];
  99.     D[J] := T;
  100.     Inc(T, D[i]);
  101.     Byte(Dest[S]) := Byte(Source[S]) xor D[T];
  102.   end;
  103. end;
  105. end.

Publicado por luchin en 12:09

0 comentarios:

Publicar un comentario

Suscribirse a: Enviar comentarios (Atom)
Twitter Delicious Facebook Digg Stumbleupon Favorites More