在.net中,由于.net framework 封裝了常見的加密算法,因此實(shí)現(xiàn)標(biāo)準(zhǔn)的md5算法只需要短短幾行代碼即可實(shí)現(xiàn):

 public string md5(string strpassword)
  {
   
     md5cryptoserviceprovider hashmd5;
　 hashmd5 = new md5cryptoserviceprovider();
    return bitconverter.tostring(hashmd5.computehash(encoding.default.getbytes(strpassword))).replace("-","").tolower();
   }

,但是當(dāng)加密字符串含有中文或者其它雙字節(jié)字符時(shí),這種算法的結(jié)果與目前網(wǎng)上流行的asp寫的md5算法的結(jié)果卻不一致,這主要是由于目前網(wǎng)上流行的asp寫的md5加密算法,存在一個(gè)缺陷,它使用了mid函數(shù)，取出的是“字符”，而正確的做法應(yīng)該是取出字節(jié),因此當(dāng)加密字符串有雙字節(jié)字符時(shí),結(jié)果會(huì)與標(biāo)準(zhǔn)的md5算法不一致.。但是由于在asp向asp.net的系統(tǒng)進(jìn)行升級(jí)的過程中，已經(jīng)向數(shù)據(jù)庫內(nèi)寫入了大量以前asp算法加密的密碼，為了使新系統(tǒng)能夠與原來的系統(tǒng)完全兼容，因此只有在.net 環(huán)境下實(shí)現(xiàn)與原來asp算法完全一致的md5算法。我的實(shí)現(xiàn)思路如下：

1、先用正則表達(dá)式對(duì)要加密的字符串進(jìn)行判斷，是否含有雙字節(jié)字符。

2、如果含有雙字節(jié)字符，調(diào)用實(shí)現(xiàn)與asp算法一致的非托管com組件進(jìn)行處理。（這個(gè)組件只需要將原asp加密算法代碼進(jìn)行適當(dāng)修改，然后加入vb6中進(jìn)行編譯即可得到）。

3、否則直接調(diào)用.net的標(biāo)準(zhǔn)md5加密算法。

可能有的朋友會(huì)問到，為什么不都直接調(diào)用com組件來加密呢？這主要是從性能角度考慮的，由于調(diào)用非托管com組件，.net需要生成一個(gè)代理類與之交互，所以在性能方面要遠(yuǎn)遠(yuǎn)低于.net內(nèi)置的函數(shù)。

下面給出所有代碼：

原asp加密代碼：

<%

private const bits_to_a_byte = 8
private const bytes_to_a_word = 4
private const bits_to_a_word = 32

private m_lonbits(30)
private m_l2power(30)
 
    m_lonbits(0) = clng(1)
    m_lonbits(1) = clng(3)
    m_lonbits(2) = clng(7)
    m_lonbits(3) = clng(15)
    m_lonbits(4) = clng(31)
    m_lonbits(5) = clng(63)
    m_lonbits(6) = clng(127)
    m_lonbits(7) = clng(255)
    m_lonbits(8) = clng(511)
    m_lonbits(9) = clng(1023)
    m_lonbits(10) = clng(2047)
    m_lonbits(11) = clng(4095)
    m_lonbits(12) = clng(8191)
    m_lonbits(13) = clng(16383)
    m_lonbits(14) = clng(32767)
    m_lonbits(15) = clng(65535)
    m_lonbits(16) = clng(131071)
    m_lonbits(17) = clng(262143)
    m_lonbits(18) = clng(524287)
    m_lonbits(19) = clng(1048575)
    m_lonbits(20) = clng(2097151)
    m_lonbits(21) = clng(4194303)
    m_lonbits(22) = clng(8388607)
    m_lonbits(23) = clng(16777215)
    m_lonbits(24) = clng(33554431)
    m_lonbits(25) = clng(67108863)
    m_lonbits(26) = clng(134217727)
    m_lonbits(27) = clng(268435455)
    m_lonbits(28) = clng(536870911)
    m_lonbits(29) = clng(1073741823)
    m_lonbits(30) = clng(2147483647)
   
    m_l2power(0) = clng(1)
    m_l2power(1) = clng(2)
    m_l2power(2) = clng(4)
    m_l2power(3) = clng(8)
    m_l2power(4) = clng(16)
    m_l2power(5) = clng(32)
    m_l2power(6) = clng(64)
    m_l2power(7) = clng(128)
    m_l2power(8) = clng(256)
    m_l2power(9) = clng(512)
    m_l2power(10) = clng(1024)
    m_l2power(11) = clng(2048)
    m_l2power(12) = clng(4096)
    m_l2power(13) = clng(8192)
    m_l2power(14) = clng(16384)
    m_l2power(15) = clng(32768)
    m_l2power(16) = clng(65536)
    m_l2power(17) = clng(131072)
    m_l2power(18) = clng(262144)
    m_l2power(19) = clng(524288)
    m_l2power(20) = clng(1048576)
    m_l2power(21) = clng(2097152)
    m_l2power(22) = clng(4194304)
    m_l2power(23) = clng(8388608)
    m_l2power(24) = clng(16777216)
    m_l2power(25) = clng(33554432)
    m_l2power(26) = clng(67108864)
    m_l2power(27) = clng(134217728)
    m_l2power(28) = clng(268435456)
    m_l2power(29) = clng(536870912)
    m_l2power(30) = clng(1073741824)

private function lshift(lvalue, ishiftbits)
    if ishiftbits = 0 then
        lshift = lvalue
        exit function
    elseif ishiftbits = 31 then
        if lvalue and 1 then
            lshift = &h80000000
        else
            lshift = 0
        end if
        exit function
    elseif ishiftbits < 0 or ishiftbits > 31 then
        err.raise 6
    end if

    if (lvalue and m_l2power(31 - ishiftbits)) then
        lshift = ((lvalue and m_lonbits(31 - (ishiftbits + 1))) * m_l2power(ishiftbits)) or &h80000000
    else
        lshift = ((lvalue and m_lonbits(31 - ishiftbits)) * m_l2power(ishiftbits))
    end if
end function

private function rshift(lvalue, ishiftbits)
    if ishiftbits = 0 then
        rshift = lvalue
        exit function
    elseif ishiftbits = 31 then
        if lvalue and &h80000000 then
            rshift = 1
        else
            rshift = 0
        end if
        exit function
    elseif ishiftbits < 0 or ishiftbits > 31 then
        err.raise 6
    end if
   
    rshift = (lvalue and &h7ffffffe) / m_l2power(ishiftbits)

    if (lvalue and &h80000000) then
        rshift = (rshift or (&h40000000 / m_l2power(ishiftbits - 1)))
    end if
end function

private function rotateleft(lvalue, ishiftbits)
    rotateleft = lshift(lvalue, ishiftbits) or rshift(lvalue, (32 - ishiftbits))
end function

private function addunsigned(lx, ly)
    dim lx4
    dim ly4
    dim lx8
    dim ly8
    dim lresult
 
    lx8 = lx and &h80000000
    ly8 = ly and &h80000000
    lx4 = lx and &h40000000
    ly4 = ly and &h40000000
 
    lresult = (lx and &h3fffffff) + (ly and &h3fffffff)
 
    if lx4 and ly4 then
        lresult = lresult xor &h80000000 xor lx8 xor ly8
    elseif lx4 or ly4 then
        if lresult and &h40000000 then
            lresult = lresult xor &hc0000000 xor lx8 xor ly8
        else
            lresult = lresult xor &h40000000 xor lx8 xor ly8
        end if
    else
        lresult = lresult xor lx8 xor ly8
    end if
 
    addunsigned = lresult
end function

private function f(x, y, z)
    f = (x and y) or ((not x) and z)
end function

private function g(x, y, z)
    g = (x and z) or (y and (not z))
end function

private function h(x, y, z)
    h = (x xor y xor z)
end function

private function i(x, y, z)
    i = (y xor (x or (not z)))
end function

private sub ff(a, b, c, d, x, s, ac)
    a = addunsigned(a, addunsigned(addunsigned(f(b, c, d), x), ac))
    a = rotateleft(a, s)
    a = addunsigned(a, b)
end sub

private sub gg(a, b, c, d, x, s, ac)
    a = addunsigned(a, addunsigned(addunsigned(g(b, c, d), x), ac))
    a = rotateleft(a, s)
    a = addunsigned(a, b)
end sub

private sub hh(a, b, c, d, x, s, ac)
    a = addunsigned(a, addunsigned(addunsigned(h(b, c, d), x), ac))
    a = rotateleft(a, s)
    a = addunsigned(a, b)
end sub

private sub ii(a, b, c, d, x, s, ac)
    a = addunsigned(a, addunsigned(addunsigned(i(b, c, d), x), ac))
    a = rotateleft(a, s)
    a = addunsigned(a, b)
end sub

private function converttowordarray(smessage)
    dim lmessagelength
    dim lnumberofwords
    dim lwordarray()
    dim lbyteposition
    dim lbytecount
    dim lwordcount
   
    const modulus_bits = 512
    const congruent_bits = 448
   
    lmessagelength = len(smessage)
   
    lnumberofwords = (((lmessagelength + ((modulus_bits - congruent_bits) / bits_to_a_byte)) / (modulus_bits / bits_to_a_byte)) + 1) * (modulus_bits / bits_to_a_word)
    redim lwordarray(lnumberofwords - 1)
   
    lbyteposition = 0
    lbytecount = 0
    do until lbytecount >= lmessagelength
        lwordcount = lbytecount / bytes_to_a_word
        lbyteposition = (lbytecount mod bytes_to_a_word) * bits_to_a_byte
        lwordarray(lwordcount) = lwordarray(lwordcount) or lshift(asc(mid(smessage, lbytecount + 1, 1)), lbyteposition)
        lbytecount = lbytecount + 1
    loop

    lwordcount = lbytecount / bytes_to_a_word
    lbyteposition = (lbytecount mod bytes_to_a_word) * bits_to_a_byte

    lwordarray(lwordcount) = lwordarray(lwordcount) or lshift(&h80, lbyteposition)

    lwordarray(lnumberofwords - 2) = lshift(lmessagelength, 3)
    lwordarray(lnumberofwords - 1) = rshift(lmessagelength, 29)
   
    converttowordarray = lwordarray
end function

private function wordtohex(lvalue)
    dim lbyte
    dim lcount
   
    for lcount = 0 to 3
        lbyte = rshift(lvalue, lcount * bits_to_a_byte) and m_lonbits(bits_to_a_byte - 1)
        wordtohex = wordtohex & right("0" & hex(lbyte), 2)
    next
end function

public function calcmd5(smessage)
    dim x
    dim k
    dim aa
    dim bb
    dim cc
    dim dd
    dim a
    dim b
    dim c
    dim d
   
    const s11 = 7
    const s12 = 12
    const s13 = 17
    const s14 = 22
    const s21 = 5
    const s22 = 9
    const s23 = 14
    const s24 = 20
    const s31 = 4
    const s32 = 11
    const s33 = 16
    const s34 = 23
    const s41 = 6
    const s42 = 10
    const s43 = 15
    const s44 = 21

    x = converttowordarray(smessage)
   
    a = &h67452301
    b = &hefcdab89
    c = &h98badcfe
    d = &h10325476

    for k = 0 to ubound(x) step 16
        aa = a
        bb = b
        cc = c
        dd = d
   
        ff a, b, c, d, x(k + 0), s11, &hd76aa478
        ff d, a, b, c, x(k + 1), s12, &he8c7b756
        ff c, d, a, b, x(k + 2), s13, &h242070db
        ff b, c, d, a, x(k + 3), s14, &hc1bdceee
        ff a, b, c, d, x(k + 4), s11, &hf57c0faf
        ff d, a, b, c, x(k + 5), s12, &h4787c62a
        ff c, d, a, b, x(k + 6), s13, &ha8304613
        ff b, c, d, a, x(k + 7), s14, &hfd469501
        ff a, b, c, d, x(k + 8), s11, &h698098d8
        ff d, a, b, c, x(k + 9), s12, &h8b44f7af
        ff c, d, a, b, x(k + 10), s13, &hffff5bb1
        ff b, c, d, a, x(k + 11), s14, &h895cd7be
        ff a, b, c, d, x(k + 12), s11, &h6b901122
        ff d, a, b, c, x(k + 13), s12, &hfd987193
        ff c, d, a, b, x(k + 14), s13, &ha679438e
        ff b, c, d, a, x(k + 15), s14, &h49b40821
   
        gg a, b, c, d, x(k + 1), s21, &hf61e2562
        gg d, a, b, c, x(k + 6), s22, &hc040b340
        gg c, d, a, b, x(k + 11), s23, &h265e5a51
        gg b, c, d, a, x(k + 0), s24, &he9b6c7aa
        gg a, b, c, d, x(k + 5), s21, &hd62f105d
        gg d, a, b, c, x(k + 10), s22, &h2441453
        gg c, d, a, b, x(k + 15), s23, &hd8a1e681
        gg b, c, d, a, x(k + 4), s24, &he7d3fbc8
        gg a, b, c, d, x(k + 9), s21, &h21e1cde6
        gg d, a, b, c, x(k + 14), s22, &hc33707d6
        gg c, d, a, b, x(k + 3), s23, &hf4d50d87
        gg b, c, d, a, x(k + 8), s24, &h455a14ed
        gg a, b, c, d, x(k + 13), s21, &ha9e3e905
        gg d, a, b, c, x(k + 2), s22, &hfcefa3f8
        gg c, d, a, b, x(k + 7), s23, &h676f02d9
        gg b, c, d, a, x(k + 12), s24, &h8d2a4c8a
           
        hh a, b, c, d, x(k + 5), s31, &hfffa3942
        hh d, a, b, c, x(k + 8), s32, &h8771f681
        hh c, d, a, b, x(k + 11), s33, &h6d9d6122
        hh b, c, d, a, x(k + 14), s34, &hfde5380c
        hh a, b, c, d, x(k + 1), s31, &ha4beea44
        hh d, a, b, c, x(k + 4), s32, &h4bdecfa9
        hh c, d, a, b, x(k + 7), s33, &hf6bb4b60
        hh b, c, d, a, x(k + 10), s34, &hbebfbc70
        hh a, b, c, d, x(k + 13), s31, &h289b7ec6
        hh d, a, b, c, x(k + 0), s32, &heaa127fa
        hh c, d, a, b, x(k + 3), s33, &hd4ef3085
        hh b, c, d, a, x(k + 6), s34, &h4881d05
        hh a, b, c, d, x(k + 9), s31, &hd9d4d039
        hh d, a, b, c, x(k + 12), s32, &he6db99e5
        hh c, d, a, b, x(k + 15), s33, &h1fa27cf8
        hh b, c, d, a, x(k + 2), s34, &hc4ac5665
   
        ii a, b, c, d, x(k + 0), s41, &hf4292244
        ii d, a, b, c, x(k + 7), s42, &h432aff97
        ii c, d, a, b, x(k + 14), s43, &hab9423a7
        ii b, c, d, a, x(k + 5), s44, &hfc93a039
        ii a, b, c, d, x(k + 12), s41, &h655b59c3
        ii d, a, b, c, x(k + 3), s42, &h8f0ccc92
        ii c, d, a, b, x(k + 10), s43, &hffeff47d
        ii b, c, d, a, x(k + 1), s44, &h85845dd1
        ii a, b, c, d, x(k + 8), s41, &h6fa87e4f
        ii d, a, b, c, x(k + 15), s42, &hfe2ce6e0
        ii c, d, a, b, x(k + 6), s43, &ha3014314
        ii b, c, d, a, x(k + 13), s44, &h4e0811a1
        ii a, b, c, d, x(k + 4), s41, &hf7537e82
        ii d, a, b, c, x(k + 11), s42, &hbd3af235
        ii c, d, a, b, x(k + 2), s43, &h2ad7d2bb
        ii b, c, d, a, x(k + 9), s44, &heb86d391
   
        a = addunsigned(a, aa)
        b = addunsigned(b, bb)
        c = addunsigned(c, cc)
        d = addunsigned(d, dd)
    next
   
    calcmd5 = lcase(wordtohex(a) & wordtohex(b) & wordtohex(c) & wordtohex(d))
end function
%>

這段代碼，只需要復(fù)制到vb activex dll項(xiàng)目中，將變量初始化的代碼移到類初始化的位置編譯即可生成同樣算法的非托管com組件。

在.net中，引用com組件，并使用如下方法進(jìn)行調(diào)用：

using system;
using system.text;
using system.text.regularexpressions;
using system.security.cryptography;
using md5;
namespace yournamespace

{

public class aspmd5

  {

 /// <summary>
  /// 與asp兼容的md5加密算法
  /// </summary>
  /// <param name="strpassword"></param>
  /// <returns></returns>
  public string md5(string strpassword)
  {
   
   
   system.text.regularexpressions.regex regexp = new regex(@"[^x00-xff]"); //匹配漢字

   if(regexp.ismatch(strpassword))
   {
    //引用com組件,實(shí)現(xiàn)與asp兼容的md5算法
    md5.securitymd5class obj = new securitymd5class(); //注意：在vb類模塊里，這里的類名為securitymd5class
    return obj. calcmd5(strpassword).tolower();
   }
   else
   {
    //標(biāo)準(zhǔn)md5算法
   md5cryptoserviceprovider hashmd5;
　　  hashmd5 = new md5cryptoserviceprovider();
    return bitconverter.tostring(hashmd5.computehash(encoding.default.getbytes(strpassword))).replace("-","").tolower();
   }
   
  }

  }

}

由于時(shí)間倉促，可能文章中有寫得不夠準(zhǔn)確的地方，歡迎批評(píng)指正，同時(shí)如果其它朋友有更好的實(shí)現(xiàn)方法，歡迎來信交流。