和md5.asp结果一样的Delphi加密代码Delphi教程

  今天我有提过md5.asp因为设计上的缺陷，在对双字节字符(比方说中文)进行加密的时候会和标准的md5算法(.Net /IndyHashMessageDigest5 / md5.pas，这三者计算结果相同，同为以字节为单位计算岀的结果)结果有出入。

  其原因在于md5.asp使用mid函数，取出的是“字符”，而正确的做法应该是取出字节,可是论坛数据库(比方说dvbbs7)中的数据已经是md5.asp的加密结果，所以我们只能将错就错，为我们的程序重写一个和md5.asp一样的加密过程
  >>>> 被广泛使用的MD5.asp中似乎存在缺陷

  我今天总算是用Delphi写出来了
虽然不知道asc函数得到的结果是否正确代码——我的目标是和md5.asp结果一样，现在缺的不就是这个有缺陷的程序吗？

unit AMD5;

interface

        ////////////////////////////////////////////
        //  文件名 : AMD5.pas                     //
        //   功能  : 与md5.asp计算结果相同        //
        //   作者  : 由ScriptBaby改编自md5.asp    //
        // 完成时间: 2004-07-21                   //
        ////////////////////////////////////////////

              //请转载者保留以上信息，谢谢//

uses
  SysUtils;

type
  arrlongword = array of longword;

type
  sMD5 = class
    class function RotateLeft(const lValue, Bits: longword): longword;
    class function MD5(const sMessage: string; const sType: boolean = false): string;
    class function ConvToWord(const sMessage: string): arrlongword; overload;
    class function ConvToWord(const sMessage: WideString): arrlongword; overload;
    class function WordToHex(const lValue: longword): string;
  end;

implementation

const
  BITS_TO_A_BYTE = 8;
  BYTES_TO_A_WORD = 4;
  BITS_TO_A_WORD = 32;

  cAA = $67452301;
  cBB = $EFCDAB89;
  cCC = $98BADCFE;
  cDD = $10325476;

  MODULUS_BITS = 512;
  CONGRUENT_BITS = 448;

{ sMD5 }

class function sMD5.ConvToWord(const sMessage: WideString): arrlongword;
var
  lMessageLength,      
  lNumberOfWords,      
  lBytePosition,
  lByteCount,          
  lWordCount: longword;
  lWordArray: arrlongword;

  { Function }
  function Asc(const t: WideChar): Smallint;
  var
    s: string;
    a: Smallint;
  begin
     s := t;

     a := Smallint(s[1]);
     case Length(s) of
       2:
       begin
         a := a shl 8;
         a := a + Smallint(s[2]);
       end
     else ;
     end;

     Result := a;
  end;

[page]

begin
  lMessageLength := Length(sMessage);

  lNumberOfWords := (((lMessageLength + ((MODULUS_BITS - CONGRUENT_BITS) div BITS_TO_A_BYTE)) div (MODULUS_BITS div BITS_TO_A_BYTE)) + 1) * (MODULUS_BITS div BITS_TO_A_WORD);

  SetLength(lWordArray, lNumberOfWords);

  lByteCount := 0;
  While lByteCount < lMessageLength do begin
    lWordCount := lByteCount div BYTES_TO_A_WORD;
    lBytePosition := (lByteCount Mod BYTES_TO_A_WORD) * BITS_TO_A_BYTE;
    lWordArray[lWordCount] := lWordArray[lWordCount] Or longword(Asc(sMessage[lByteCount + 1]) shl lBytePosition);
    lByteCount := lByteCount + 1;
  end;

  lWordCount := lByteCount div BYTES_TO_A_WORD;
  lBytePosition := (lByteCount Mod BYTES_TO_A_WORD) * BITS_TO_A_BYTE;

  lWordArray[lWordCount] := lWordArray[lWordCount] or ($80 shl lBytePosition);

  lWordArray[lNumberOfWords - 2] := lMessageLength shl 3;
  lWordArray[lNumberOfWords - 1] := lMessageLength shr 29;

  Result := lWordArray;

end;

class function sMD5.ConvToWord(const sMessage: string): arrlongword;
begin
  Result := ConvToWord(WideString(sMessage));
end;

class function sMD5.MD5(const sMessage: string;
  const sType: boolean = false): string;
const
  S11 = 7; 
  S12 = 12;
  S13 = 17;
  S14 = 22;
  S21 = 5; 
  S22 = 9; 
  S23 = 14;
  S24 = 20;
  S31 = 4; 
  S32 = 11;
  S33 = 16;
  S34 = 23;
  S41 = 6; 
  S42 = 10;
  S43 = 15;
  S44 = 21;

var
  k: integer;
  AA, BB, CC, DD, a, b, c, d: longword;
  x: arrlongword;
  s: string;
 
  { functions }

  function md5_F(const x, y, z: longword): longword;
  begin
    Result := (x And y) Or ((Not x) And z);
  end;

  function md5_G(const x, y, z: longword): longword;
  begin
    Result := (x And z) Or (y And (Not z));
  end;

  function md5_H(const x, y, z: longword): longword;
  begin
    Result := (x Xor y Xor z);
  end;

  function md5_I(const x, y, z: longword): longword;
  begin
    Result := (y Xor (x Or (Not z)));
  end;

  procedure md5_FF(var a: longword; const b, c, d, x, s, ac: longword);
  begin
    a := a + md5_F(b, c, d) + x + ac;
    a := RotateLeft(a, s);
    a := a + b;
  end;

  procedure md5_GG(var a: longword; const b, c, d, x, s, ac: longword);
  begin
    a := a + md5_G(b, c, d) + x + ac;
    a := RotateLeft(a, s);
    a := a + b;
  end;