SHA1加密算法实现与解密

============================= SHA1 ิดย๋ ===============================================================

{
  ***************************************************   
  *   A   binary   compatible   SHA1   implementation                   *   
  *   written   by   Dave   Barton   (davebarton@bigfoot.com)   *   
  ***************************************************   
  *   160bit   hash   size                                                                 *   
  ***************************************************   
  }
unit SHA1;

interface

uses
  Sysutils, Tools;

  type
    TSHA1Digest = array[0..19] of Byte;
    TSHA1Context = record
        Hash: array[0..4] of DWord;
        Hi, Lo: Integer;
        Buffer: array[0..63] of Byte;
        Index: Integer;
    end;
  function SHA1SelfTest: Boolean;
  procedure SHA1Init(var Context: TSHA1Context);
  procedure SHA1Update(var Context: TSHA1Context; Buffer: Pointer; Len: Integer);
  procedure SHA1Final(var Context: TSHA1Context; var Digest: TSHA1Digest);

    
//******************************************************************************   
implementation   
{$R-}   
    
function SHA1SelfTest: Boolean;
const   
  s: String = 'abc';
  OutDigest: TSHA1Digest =
    ($a9,$99,$3e,$36,$47,$06,$81,$6a,$ba,$3e,$25,$71,$78,$50,$c2,$6c,$9c,$d0,$d8,$9d);
var
  Context: TSHA1Context;
  Digest: TSHA1Digest;
begin
  SHA1Init(Context);
  SHA1Update(Context, @s[1], Length(s));
  SHA1Final(Context, Digest);
  if CompareMem(@Digest, @OutDigest, Sizeof(Digest)) then
    Result:= True
  else
    Result:= False;
end;

function F1(x, y, z: DWord): DWord;
begin   
  Result:= z xor (x and (y xor z));
end;

function F2(x, y, z: DWord): DWord;
begin