Question

所以我读到了为了解密

 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

我需要将其拆分为5个通道并解决单字节XOR键，获得daeb1551e7的候选键。我的问题是你怎么知道你需要分成多少个不同的“通道”以及分裂发生的位置。

Answer 1

这就是我得到的，它在javascript中：

var cryptmsg="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";
var key="daeb1551e7";
var hexmsg=Array.from(cryptmsg);
var hexkey=Array.from(key);
var channels=[

];

while(hexkey.length){
  var buffer=hexkey.splice(0,2);
  var channel={
    msg:[],
    key:buffer.join("")
  };
  channels.push(channel);
}

var chanIndex=0;
while(hexmsg.length){
  var buffer=hexmsg.splice(0,2);
  channels[chanIndex].msg.push(buffer);
  chanIndex++;
  chanIndex=chanIndex%5;
}
var channelResults=channels.map(function(channel){
  var nkey=parseInt(channel.key,16);
  return channel.msg.map(
    function(pair){return pair[0]+pair[1];}
  ).map(function(hexchar){
    var nchar=parseInt(hexchar,16);
    var ndec=nchar^nkey;
    return String.fromCharCode(ndec);
  });
});
var decodedMsg=[];
chanIndex=0
while(1){
  var chresult=channelResults[chanIndex];
  if(chresult.length<=0)break;
  decodedMsg.push(chresult.shift());
  chanIndex++;
  chanIndex=chanIndex%5;
}
decodedMsg.join("");

产生的已解码消息：

/*
Bletchey Park rejoices in the fact that, until fairly recently, it was probably Britain's best kept secret. This is because of the secrecy surrounding all the activities carried on here during World War Two was of vital importance to our national security and ultimate victory.
*/

事实证明，每个频道都拥有自己的一个字节密钥，并且＆＃39;消息＆＃39;对于特定信道，从原始加密消息（即，字节1到信道1，字节2到信道2，...，字节6到信道1）循环的字节（十六对）聚合。使用一个字节键解码。然后通过颠倒我们整理的过程来重建最终解密的消息。加密的消息字节进入其通道。

更新

紧凑版：

var cryptmsg="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";
var key="daeb1551e7";
var aCryptMsg=Array.prototype.slice.call(cryptmsg);
var aKey=Array.prototype.slice.call(key);
var chanKey=[];
var chanIndex=0;
var aDecryptMsg=[];
function dec(nkey,ncrypt){
    var ndec=nkey^ncrypt;
    return String.fromCharCode(ndec); 
}
while(aKey.length){
  var buffer=aKey.splice(0,2);
  var nkey=parseInt(buffer.join(""),16);
  chanKey.push(nkey);
}
while(aCryptMsg.length){
  var buffer=aCryptMsg.splice(0,2);
  var ncrypt=parseInt(buffer.join(""),16);
  var debuf=dec(chanKey[chanIndex],ncrypt);
  aDecryptMsg.push(debuf);
  chanIndex=(++chanIndex)%5;
}
aDecryptMsg.join("");

/*
Bletchey Park rejoices in the fact that, until fairly recently, it was probably Britain's best kept secret. This is because of the secrecy surrounding all the activities carried on here during World War Two was of vital importance to our national security and ultimate victory.
*/

Answer 2

your encrypted message的解决方案（参见comment）：

var cryptmsg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
var aCryptMsg=Array.from(cryptmsg);
var channelCount=8;
var channel=[];
var chanIndex=0;
function dec(nkey,ncrypt){
  var ndec=nkey^ncrypt;
  return ndec;
}

for(var i=0; i<channelCount; i++){
  channel[i]=[];
}
while(aCryptMsg.length){
  var buffer=aCryptMsg.splice(0,2).join("");
  var ncrypt=parseInt(buffer,16);
  channel[chanIndex].push(ncrypt);
  chanIndex=(++chanIndex)%channelCount;
}
var goody=Object.create(null);
var alphanumerics=[[0x30,0x39],[0x41,0x5a],[0x61,0x7a]];
var alphabetical=[[0x41,0x5a],[0x61,0x7a]];
var currentRanges=alphanumerics;
currentRanges.forEach(function(range){
  var indexStart=range[0];
  var indexEnd=range[1];
  for (var i=indexStart; i<=indexEnd; i++){
    //table.push(String.fromCharCode(i));
    var ch=String.fromCharCode(i);
    goody[ch]=1;
  }   
});
(" ,.;:!\"'").split("").forEach(ch=>goody[ch]=1);

function findKeyCandidate(byteArray){
  var keyResults=[];
  for (var key=0; key<256; key++){
    keyResults[key]=0;
    byteArray.forEach(function(ncrypt){
      var ndec=dec(key,ncrypt);
      var dchar=String.fromCharCode(ndec);
      if(goody[dchar]){
        keyResults[key]++;
      }
    });
  }
  keyResults=keyResults.map(function(count,index){
    return {key:index,count:count};
  });
  keyResults.sort(function(a,b){
    return a.count-b.count;
  });
  return keyResults.pop().key;
}

var chanKey=channel.map(findKeyCandidate);
chanIndex=0;
var aDecrypMsg=[];
while(channel[chanIndex].length>0){
  var ncrypt=channel[chanIndex].shift();
  var nkey=chanKey[chanIndex];
  var ndec=dec(nkey,ncrypt);
  aDecrypMsg.push(ndec);
  chanIndex=(++chanIndex)%channelCount;
}
aDecrypMsg.map(function(byte){return String.fromCharCode(byte)}).join("");

解码结果：

/*
your flag is: 93ea36e84ba568b6590ec3b147d7a01e45b66202

On 17 March 1975, the proposed DES was published in the Federal Register. Public comments were requested, and in the following year two open workshops were held to discuss the proposed standard. There was some criticism from various parties, including from public-key cryptography pioneers Martin Hellman and Whitfield Diffie, citing a shortened key length and the mysterious "S-boxes" as evidence of improper interference from the NSA. The suspicion was that the algorithm had been covertly weakened by the intelligence agency so that they - but no-one else - could easily read encrypted messages. Alan Konheim (one of the designers of DES) commented, "We sent the S-boxes off to Washington. They came back and were all different." The United States Senate Select Committee on Intelligence reviewed the NSA's actions to determine whether there had been any improper involvement. In the unclassified summary of their findings, published in 1978, the Committee wrote:

    In the development of DES, NSA convinced IBM that a reduced key size was sufficient; indirectly assisted in the development of the S-box structures; and certified that the final DES algorithm was, to the best of their knowledge, free from any statistical or mathematical weakness.

However, it also found that

    NSA did not tamper with the design of the algorithm in any way. IBM invented and designed the algorithm, made all pertinent decisions regarding it, and concurred that the agreed upon key size was more than adequate for all commercial applications for which the DES was intended.

Another member of the DES team, Walter Tuchman, stated "We developed the DES algorithm entirely within IBM using IBMers. The NSA did not dictate a single wire!" In contrast, a declassified NSA book on cryptologic history states:

    In 1973 NBS solicited private industry for a data encryption standard (DES). The first offerings were disappointing, so NSA began working on its own algorithm. Then Howard Rosenblum, deputy director for research and engineering, discovered that Walter Tuchman of IBM was working on a modification to Lucifer for general use. NSA gave Tuchman a clearance and brought him in to work jointly with the Agency on his Lucifer modification."

and

    NSA worked closely with IBM to strengthen the algorithm against all except brute force attacks and to strengthen substitution tables, called S-boxes. Conversely, NSA tried to convince IBM to reduce the length of the key from 64 to 48 bits. Ultimately they compromised on a 56-bit key.

Some of the suspicions about hidden weaknesses in the S-boxes were allayed in 1990, with the independent discovery and open publication by Eli Biham and Adi Shamir of differential cryptanalysis, a general method for breaking block ciphers. The S-boxes of DES were much more resistant to the attack than if they had been chosen at random, strongly suggesting that IBM knew about the technique in the 1970s. This was indeed the case; in 1994, Don Coppersmith published some of the original design criteria for the S-boxes. According to Steven Levy, IBM Watson researchers discovered differential cryptanalytic attacks in 1974 and were asked by the NSA to keep the technique secret. Coppersmith explains IBM's secrecy decision by saying, "that was because [differential cryptanalysis] can be a very powerful tool, used against many schemes, and there was concern that such information in the public domain could adversely affect national security." Levy quotes Walter Tuchman: "[t]hey asked us to stamp all our documents confidential... We actually put a number on each one and locked them up in safes, because they were considered U.S. government classified. They said do it. So I did it". Bruce Schneier observed that "It took the academic community two decades to figure out that the NSA 'tweaks' actually improved the security of DES."
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解码十六进制xor加密

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