MD5Sum算法如何工作？

Md5sum用於檢查ubuntu的iso映像的完整性。它是如何工作的？MD5Sum算法如何工作？

2009-06-15 TwiggedToday

這裏的大部分答案都解釋了MD5的工作原理，而不是MD5Sum的工作原理。例如，它是否將文件大小與文件中每個咬合的每個第一位相結合？它是否直接處理整個文件？我對這些東西感興趣，我認爲提問者也是。散列可以在許多不同的事情上完成，但它如何應用於文件以產生校驗和是不同的 – Sprague 2010-07-01 19:22:38

所有md5sum都執行MD5。它可能會對多個文件起作用，但仍會爲每個文件生成一個MD5。絕對沒有區別。 – defines 2013-07-30 22:48:04

算法消息摘要5或MD5，它是一種單向加密散列函數。 MD5對「消息」（例如，iso圖像的二進制數據）執行許多二進制操作以計算128位「散列」。

檢查下載的軟件包（如ubuntu）的完整性非常有用，因爲如果軟件包與經過身份驗證的源完全相同，那麼生成MD5哈希將是相同的。如果下載中出現錯誤（來自網絡干擾等），或者您下載了一個看起來像ubuntu但含有其他代碼/任何內容的惡意軟件包，那麼MD5將不匹配，您會知道有些事情是不同的，你應該從另一個來源再次下載。

UPDATE

如果上面沒有解釋「它是如何工作」爲你毫不誇張的是，這是我自己的JavaScript實現MD5算法：

/** 
* JavaScript Class Implementation of RSA Data Security, Inc. 
* Message Digest 5 (MD5) Algorithm, as defined in RFC 1321. 
* 
* @author Dustin C. Fineout <[email protected]> 
* @created 10/10/2009 11:23:29 AM 
* @modified 10/10/2009 12:34:56 PM 
* @version 0.1 WORKING 
**/ 

/** 
* Usage example: 
* var md5 = new MD5(); 
* alert(md5.hash('Dustin Fineout')); // 8844be37f4e8b3973b48b95b0c69f0b1 
**/ 
function MD5() 
{ 
    this.F = function(x,y,z) { return (x & y) | ((~x) & z); }; 
    this.G = function(x,y,z) { return (x & z) | (y & (~z)); }; 
    this.H = function(x,y,z) { return (x^y^z); }; 
    this.I = function(x,y,z) { return (y^(x | (~z))); }; 
    this.C = function(q,a,b,x,s,ac) { return this.addu(this.rol(this.addu(this.addu(a,q),this.addu(x,ac)),s),b); }; 
    this.FF = function(a,b,c,d,x,s,ac) { return this.C((b & c) | ((~b) & d),a,b,x,s,ac); }; 
    this.GG = function(a,b,c,d,x,s,ac) { return this.C((b & d) | (c & (~d)),a,b,x,s,ac); }; 
    this.HH = function(a,b,c,d,x,s,ac) { return this.C(b^c^d,a,b,x,s,ac); }; 
    this.II = function(a,b,c,d,x,s,ac) { return this.C(c^(b | (~d)),a,b,x,s,ac); }; 

    this.hash = function(message) 
    { 
    var xl,x=[],k,aa,bb,cc,dd,a=0x67452301,b=0xEFCDAB89,c=0x98BADCFE,d=0x10325476; 
    x = this.convertToWordArray(this.utf8Encode(message)); 
    xl = x.length; 
    for (var j = 0; j < xl; j += 16) { 
     aa=a; bb=b; cc=c; dd=d; 
     a=this.FF(a,b,c,d,x[j+0],7,0xD76AA478); 
     d=this.FF(d,a,b,c,x[j+1],12,0xE8C7B756); 
     c=this.FF(c,d,a,b,x[j+2],17,0x242070DB); 
     b=this.FF(b,c,d,a,x[j+3],22,0xC1BDCEEE); 
     a=this.FF(a,b,c,d,x[j+4],7,0xF57C0FAF); 
     d=this.FF(d,a,b,c,x[j+5],12,0x4787C62A); 
     c=this.FF(c,d,a,b,x[j+6],17,0xA8304613); 
     b=this.FF(b,c,d,a,x[j+7],22,0xFD469501); 
     a=this.FF(a,b,c,d,x[j+8],7,0x698098D8); 
     d=this.FF(d,a,b,c,x[j+9],12,0x8B44F7AF); 
     c=this.FF(c,d,a,b,x[j+10],17,0xFFFF5BB1); 
     b=this.FF(b,c,d,a,x[j+11],22,0x895CD7BE); 
     a=this.FF(a,b,c,d,x[j+12],7,0x6B901122); 
     d=this.FF(d,a,b,c,x[j+13],12,0xFD987193); 
     c=this.FF(c,d,a,b,x[j+14],17,0xA679438E); 
     b=this.FF(b,c,d,a,x[j+15],22,0x49B40821); 
     a=this.GG(a,b,c,d,x[j+1],5,0xF61E2562); 
     d=this.GG(d,a,b,c,x[j+6],9,0xC040B340); 
     c=this.GG(c,d,a,b,x[j+11],14,0x265E5A51); 
     b=this.GG(b,c,d,a,x[j+0],20,0xE9B6C7AA); 
     a=this.GG(a,b,c,d,x[j+5],5,0xD62F105D); 
     d=this.GG(d,a,b,c,x[j+10],9,0x2441453); 
     c=this.GG(c,d,a,b,x[j+15],14,0xD8A1E681); 
     b=this.GG(b,c,d,a,x[j+4],20,0xE7D3FBC8); 
     a=this.GG(a,b,c,d,x[j+9],5,0x21E1CDE6); 
     d=this.GG(d,a,b,c,x[j+14],9,0xC33707D6); 
     c=this.GG(c,d,a,b,x[j+3],14,0xF4D50D87); 
     b=this.GG(b,c,d,a,x[j+8],20,0x455A14ED); 
     a=this.GG(a,b,c,d,x[j+13],5,0xA9E3E905); 
     d=this.GG(d,a,b,c,x[j+2],9,0xFCEFA3F8); 
     c=this.GG(c,d,a,b,x[j+7],14,0x676F02D9); 
     b=this.GG(b,c,d,a,x[j+12],20,0x8D2A4C8A); 
     a=this.HH(a,b,c,d,x[j+5],4,0xFFFA3942); 
     d=this.HH(d,a,b,c,x[j+8],11,0x8771F681); 
     c=this.HH(c,d,a,b,x[j+11],16,0x6D9D6122); 
     b=this.HH(b,c,d,a,x[j+14],23,0xFDE5380C); 
     a=this.HH(a,b,c,d,x[j+1],4,0xA4BEEA44); 
     d=this.HH(d,a,b,c,x[j+4],11,0x4BDECFA9); 
     c=this.HH(c,d,a,b,x[j+7],16,0xF6BB4B60); 
     b=this.HH(b,c,d,a,x[j+10],23,0xBEBFBC70); 
     a=this.HH(a,b,c,d,x[j+13],4,0x289B7EC6); 
     d=this.HH(d,a,b,c,x[j+0],11,0xEAA127FA); 
     c=this.HH(c,d,a,b,x[j+3],16,0xD4EF3085); 
     b=this.HH(b,c,d,a,x[j+6],23,0x4881D05); 
     a=this.HH(a,b,c,d,x[j+9],4,0xD9D4D039); 
     d=this.HH(d,a,b,c,x[j+12],11,0xE6DB99E5); 
     c=this.HH(c,d,a,b,x[j+15],16,0x1FA27CF8); 
     b=this.HH(b,c,d,a,x[j+2],23,0xC4AC5665); 
     a=this.II(a,b,c,d,x[j+0],6,0xF4292244); 
     d=this.II(d,a,b,c,x[j+7],10,0x432AFF97); 
     c=this.II(c,d,a,b,x[j+14],15,0xAB9423A7); 
     b=this.II(b,c,d,a,x[j+5],21,0xFC93A039); 
     a=this.II(a,b,c,d,x[j+12],6,0x655B59C3); 
     d=this.II(d,a,b,c,x[j+3],10,0x8F0CCC92); 
     c=this.II(c,d,a,b,x[j+10],15,0xFFEFF47D); 
     b=this.II(b,c,d,a,x[j+1],21,0x85845DD1); 
     a=this.II(a,b,c,d,x[j+8],6,0x6FA87E4F); 
     d=this.II(d,a,b,c,x[j+15],10,0xFE2CE6E0); 
     c=this.II(c,d,a,b,x[j+6],15,0xA3014314); 
     b=this.II(b,c,d,a,x[j+13],21,0x4E0811A1); 
     a=this.II(a,b,c,d,x[j+4],6,0xF7537E82); 
     d=this.II(d,a,b,c,x[j+11],10,0xBD3AF235); 
     c=this.II(c,d,a,b,x[j+2],15,0x2AD7D2BB); 
     b=this.II(b,c,d,a,x[j+9],21,0xEB86D391); 
     a=this.addu(a,aa); b=this.addu(b,bb); c=this.addu(c,cc); d=this.addu(d,dd); 
    } 
    return (this.wordToHex(a)+this.wordToHex(b)+this.wordToHex(c)+this.wordToHex(d)).toLowerCase(); 
    }; 

    this.test = function() 
    { 
    if (this.hash('Dustin Fineout') == '8844be37f4e8b3973b48b95b0c69f0b1') { 
     return true; 
    } 
    return false; 
    }; 

    this.addu = function(x, y) 
    { 
    var ls = (x & 0xFFFF) + (y & 0xFFFF); 
    return (((x >> 16) + (y >> 16) + (ls >> 16)) << 16) | (ls & 0xFFFF); 
    }; 

    this.rol = function(v, s) 
    { 
    return (v << s) | (v >>> (32 - s)); 
    }; 

    this.utf8Encode = function(str) 
    { 
    return unescape(encodeURIComponent(str)); 
    }; 

    this.convertToWordArray = function(str) 
    { 
    var lWordCount; 
    var lMessageLength = str.length; 
    var lNumberOfWords_temp1=lMessageLength + 8; 
    var lNumberOfWords_temp2=(lNumberOfWords_temp1-(lNumberOfWords_temp1 % 64))/64; 
    var lNumberOfWords = (lNumberOfWords_temp2+1)*16; 
    var lWordArray=new Array(lNumberOfWords-1); 
    var lBytePosition = 0; 
    var lByteCount = 0; 
    while (lByteCount < lMessageLength) { 
     lWordCount = (lByteCount-(lByteCount % 4))/4; 
     lBytePosition = (lByteCount % 4)*8; 
     lWordArray[lWordCount] = (lWordArray[lWordCount] | (str.charCodeAt(lByteCount)<<lBytePosition)); 
     lByteCount++; 
    } 
    lWordCount = (lByteCount-(lByteCount % 4))/4; 
    lBytePosition = (lByteCount % 4)*8; 
    lWordArray[lWordCount] = lWordArray[lWordCount] | (0x80<<lBytePosition); 
    lWordArray[lNumberOfWords-2] = lMessageLength<<3; 
    lWordArray[lNumberOfWords-1] = lMessageLength>>>29; 
    return lWordArray; 
    }; 

    this.wordToHex = function(lValue) 
    { 
    var wordToHexValue="",wordToHexValue_temp="",lByte,lCount; 
    for (lCount = 0;lCount<=3;lCount++) { 
     lByte = (lValue>>>(lCount*8)) & 255; 
     wordToHexValue_temp = "0" + lByte.toString(16); 
     wordToHexValue = wordToHexValue + wordToHexValue_temp.substr(wordToHexValue_temp.length-2,2); 
    } 
    return wordToHexValue; 
    }; 
}

我會很高興按照需要註釋或擴展:)另外，請注意，這不是我仍然用於JavaScript命名空間的單例模式 - 它實際上是我第一次嘗試這種模式：p Douglas Crockford提供了許多美味的單例模式。

來源

2009-06-15 17:26:17 defines

MD5Sum是一個文件checksum生成工具使用MD5作爲哈希算法。它爲用戶提供了合理的保證，即該文件未被篡改。

爲了做到這一點，用戶需要（通過shell集成或手動）處理他們自己的MD5哈希，並將其與上傳器提供的哈希進行比較。

MD5Sum散列不會保證提供校驗和的上傳器不會擺弄文件，要做到這一點，您應該相信MD5校驗和的來源（即從Ubuntu獲取校驗和而不是下載網站提供圖像）。

來源

2010-07-01 19:37:13 Sprague

MD5Sum算法如何工作？

回答

相關問題