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Javascript DES Implemenation

This is an implementation of DES (the Data Encryption Standard), an encryption algorithm which works on bits. It supports Electronic Codebook (ECB) and Cipher Block Chaining (CBC) and also includes Triple DES. This page describes how to it and provides the source code. The explanation page shows how the bit manipulations work, and gives links to some general descriptions of DES.

Usage
des (string key, string message, boolean encrypt, [integer mode, string iv])

The des function accepts an 8 character string as the key (this is 64 bits, but the algorithm only uses 56) for normal DES or a 24 character string for triple DES, a message string, a boolean to say whether the data should be encrypted or decrypted, an optional mode (0 for ECB and 1 for CBC, ECB is the default), and an optional 8 character string input vector (not used in ECB mode). It returns the cipher text as a string.

Here are several examples showing how it can be used:

//encrypt using single DES (with an 8 byte key) in CBC mode with the given input vector
des ("8bytekey", "This is the message.", 1, 1, "inputvec");
//encrypt using triple DES (with a 24 byte key) in ECB mode
des ("this is a 24 byte key !!", "This is the message.", 1);
//decrypt using single DES in ECB mode
des ("8bytekey", "2384lf&*£90LSdsf", 0);

Source Code

There is no warranty for this code and neither Laynetworks nor the auther of the code responsible for any problems arising from using it (including those caused by bugs). It has been tested to see if it produces correct output, but has not been robustly tested on different browsers, processors, or with a wide range of keys and messages. Any modifications to this code must be posted on this site. If you find any errors, bugs, security holes, or have any questions or comments please email des@shopable.co.uk.

//(c) Paul Tero, July 2001
//http://www.shopable.co.uk/des.html
//
//Optimised for performance with large blocks by Michael Hayworth, November 2001
//http://www.netdealing.com
//
//THIS SOFTWARE IS PROVIDED "AS IS" AND
//ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
//IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
//ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
//FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
//DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
//OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
//HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
//LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
//OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
//SUCH DAMAGE.

//des
//this takes the key, the message, and whether to encrypt or decrypt
function des (key, message, encrypt, mode, iv) {
  //declaring this locally speeds things up a bit
  var spfunction1 = new Array (0x1010400,0,0x10000,0x1010404,0x1010004,0x10404,0x4,0x10000,0x400,0x1010400,0x1010404,0x400,0x1000404,0x1010004,0x1000000,0x4,0x404,0x1000400,0x1000400,0x10400,0x10400,0x1010000,0x1010000,0x1000404,0x10004,0x1000004,0x1000004,0x10004,0,0x404,0x10404,0x1000000,0x10000,0x1010404,0x4,0x1010000,0x1010400,0x1000000,0x1000000,0x400,0x1010004,0x10000,0x10400,0x1000004,0x400,0x4,0x1000404,0x10404,0x1010404,0x10004,0x1010000,0x1000404,0x1000004,0x404,0x10404,0x1010400,0x404,0x1000400,0x1000400,0,0x10004,0x10400,0,0x1010004);
  var spfunction2 = new Array (0x80108020,0x80008000,0x8000,0x108020,0x100000,0x20,0x80100020,0x80008020,0x80000020,0x80108020,0x80108000,0x80000000,0x80008000,0x100000,0x20,0x80100020,0x108000,0x100020,0x80008020,0,0x80000000,0x8000,0x108020,0x80100000,0x100020,0x80000020,0,0x108000,0x8020,0x80108000,0x80100000,0x8020,0,0x108020,0x80100020,0x100000,0x80008020,0x80100000,0x80108000,0x8000,0x80100000,0x80008000,0x20,0x80108020,0x108020,0x20,0x8000,0x80000000,0x8020,0x80108000,0x100000,0x80000020,0x100020,0x80008020,0x80000020,0x100020,0x108000,0,0x80008000,0x8020,0x80000000,0x80100020,0x80108020,0x108000);
  var spfunction3 = new Array (0x208,0x8020200,0,0x8020008,0x8000200,0,0x20208,0x8000200,0x20008,0x8000008,0x8000008,0x20000,0x8020208,0x20008,0x8020000,0x208,0x8000000,0x8,0x8020200,0x200,0x20200,0x8020000,0x8020008,0x20208,0x8000208,0x20200,0x20000,0x8000208,0x8,0x8020208,0x200,0x8000000,0x8020200,0x8000000,0x20008,0x208,0x20000,0x8020200,0x8000200,0,0x200,0x20008,0x8020208,0x8000200,0x8000008,0x200,0,0x8020008,0x8000208,0x20000,0x8000000,0x8020208,0x8,0x20208,0x20200,0x8000008,0x8020000,0x8000208,0x208,0x8020000,0x20208,0x8,0x8020008,0x20200);
  var spfunction4 = new Array (0x802001,0x2081,0x2081,0x80,0x802080,0x800081,0x800001,0x2001,0,0x802000,0x802000,0x802081,0x81,0,0x800080,0x800001,0x1,0x2000,0x800000,0x802001,0x80,0x800000,0x2001,0x2080,0x800081,0x1,0x2080,0x800080,0x2000,0x802080,0x802081,0x81,0x800080,0x800001,0x802000,0x802081,0x81,0,0,0x802000,0x2080,0x800080,0x800081,0x1,0x802001,0x2081,0x2081,0x80,0x802081,0x81,0x1,0x2000,0x800001,0x2001,0x802080,0x800081,0x2001,0x2080,0x800000,0x802001,0x80,0x800000,0x2000,0x802080);
  var spfunction5 = new Array (0x100,0x2080100,0x2080000,0x42000100,0x80000,0x100,0x40000000,0x2080000,0x40080100,0x80000,0x2000100,0x40080100,0x42000100,0x42080000,0x80100,0x40000000,0x2000000,0x40080000,0x40080000,0,0x40000100,0x42080100,0x42080100,0x2000100,0x42080000,0x40000100,0,0x42000000,0x2080100,0x2000000,0x42000000,0x80100,0x80000,0x42000100,0x100,0x2000000,0x40000000,0x2080000,0x42000100,0x40080100,0x2000100,0x40000000,0x42080000,0x2080100,0x40080100,0x100,0x2000000,0x42080000,0x42080100,0x80100,0x42000000,0x42080100,0x2080000,0,0x40080000,0x42000000,0x80100,0x2000100,0x40000100,0x80000,0,0x40080000,0x2080100,0x40000100);
  var spfunction6 = new Array (0x20000010,0x20400000,0x4000,0x20404010,0x20400000,0x10,0x20404010,0x400000,0x20004000,0x404010,0x400000,0x20000010,0x400010,0x20004000,0x20000000,0x4010,0,0x400010,0x20004010,0x4000,0x404000,0x20004010,0x10,0x20400010,0x20400010,0,0x404010,0x20404000,0x4010,0x404000,0x20404000,0x20000000,0x20004000,0x10,0x20400010,0x404000,0x20404010,0x400000,0x4010,0x20000010,0x400000,0x20004000,0x20000000,0x4010,0x20000010,0x20404010,0x404000,0x20400000,0x404010,0x20404000,0,0x20400010,0x10,0x4000,0x20400000,0x404010,0x4000,0x400010,0x20004010,0,0x20404000,0x20000000,0x400010,0x20004010);
  var spfunction7 = new Array (0x200000,0x4200002,0x4000802,0,0x800,0x4000802,0x200802,0x4200800,0x4200802,0x200000,0,0x4000002,0x2,0x4000000,0x4200002,0x802,0x4000800,0x200802,0x200002,0x4000800,0x4000002,0x4200000,0x4200800,0x200002,0x4200000,0x800,0x802,0x4200802,0x200800,0x2,0x4000000,0x200800,0x4000000,0x200800,0x200000,0x4000802,0x4000802,0x4200002,0x4200002,0x2,0x200002,0x4000000,0x4000800,0x200000,0x4200800,0x802,0x200802,0x4200800,0x802,0x4000002,0x4200802,0x4200000,0x200800,0,0x2,0x4200802,0,0x200802,0x4200000,0x800,0x4000002,0x4000800,0x800,0x200002);
  var spfunction8 = new Array (0x10001040,0x1000,0x40000,0x10041040,0x10000000,0x10001040,0x40,0x10000000,0x40040,0x10040000,0x10041040,0x41000,0x10041000,0x41040,0x1000,0x40,0x10040000,0x10000040,0x10001000,0x1040,0x41000,0x40040,0x10040040,0x10041000,0x1040,0,0,0x10040040,0x10000040,0x10001000,0x41040,0x40000,0x41040,0x40000,0x10041000,0x1000,0x40,0x10040040,0x1000,0x41040,0x10001000,0x40,0x10000040,0x10040000,0x10040040,0x10000000,0x40000,0x10001040,0,0x10041040,0x40040,0x10000040,0x10040000,0x10001000,0x10001040,0,0x10041040,0x41000,0x41000,0x1040,0x1040,0x40040,0x10000000,0x10041000);

//create the 16 or 48 subkeys we will need
  var keys = des_createKeys (key);
  var m=0, i, j, temp, temp2, right1, right2, left, right, looping;
  var cbcleft, cbcleft2, cbcright, cbcright2
  var endloop, loopinc;
  var len = message.length;
  var chunk = 0;
  //set up the loops for single and triple des
  var iterations = keys.length == 32 ? 3 : 9; //single or triple des
  if (iterations == 3) {looping = encrypt ? new Array (0, 32, 2) : new Array (30, -2, -2);}
  else {looping = encrypt ? new Array (0, 32, 2, 62, 30, -2, 64, 96, 2) : new Array (94, 62, -2, 32, 64, 2, 30, -2, -2);}

message += "\0\0\0\0\0\0\0\0"; //pad the message out with null bytes
  //store the result here
  result = "";
  tempresult = "";

if (mode == 1) { //CBC mode
    cbcleft = (iv.charCodeAt(m++) << 24) | (iv.charCodeAt(m++) << 16) | (iv.charCodeAt(m++) << 8) | iv.charCodeAt(m++);
    cbcright = (iv.charCodeAt(m++) << 24) | (iv.charCodeAt(m++) << 16) | (iv.charCodeAt(m++) << 8) | iv.charCodeAt(m++);
    m=0;
  }

//loop through each 64 bit chunk of the message
  while (m < len) {
    left = (message.charCodeAt(m++) << 24) | (message.charCodeAt(m++) << 16) | (message.charCodeAt(m++) << 8) | message.charCodeAt(m++);
    right = (message.charCodeAt(m++) << 24) | (message.charCodeAt(m++) << 16) | (message.charCodeAt(m++) << 8) | message.charCodeAt(m++);

//for Cipher Block Chaining mode, xor the message with the previous result
    if (mode == 1) {if (encrypt) {left ^= cbcleft; right ^= cbcright;} else {cbcleft2 = cbcleft; cbcright2 = cbcright; cbcleft = left; cbcright = right;}}

//first each 64 but chunk of the message must be permuted according to IP
    temp = ((left >>> 4) ^ right) & 0x0f0f0f0f; right ^= temp; left ^= (temp << 4);
    temp = ((left >>> 16) ^ right) & 0x0000ffff; right ^= temp; left ^= (temp << 16);
    temp = ((right >>> 2) ^ left) & 0x33333333; left ^= temp; right ^= (temp << 2);
    temp = ((right >>> 8) ^ left) & 0x00ff00ff; left ^= temp; right ^= (temp << 8);
    temp = ((left >>> 1) ^ right) & 0x55555555; right ^= temp; left ^= (temp << 1);

left = ((left << 1) | (left >>> 31)); 
    right = ((right << 1) | (right >>> 31));

//do this either 1 or 3 times for each chunk of the message
    for (j=0; j<iterations; j+=3) {
      endloop = looping[j+1];
      loopinc = looping[j+2];
      //now go through and perform the encryption or decryption  
      for (i=looping[j]; i!=endloop; i+=loopinc) { //for efficiency
        right1 = right ^ keys[i]; 
        right2 = ((right >>> 4) | (right << 28)) ^ keys[i+1];
        //the result is attained by passing these bytes through the S selection functions
        temp = left;
        left = right;
        right = temp ^ (spfunction2[(right1 >>> 24) & 0x3f] | spfunction4[(right1 >>> 16) & 0x3f]
              | spfunction6[(right1 >>>  8) & 0x3f] | spfunction8[right1 & 0x3f]
              | spfunction1[(right2 >>> 24) & 0x3f] | spfunction3[(right2 >>> 16) & 0x3f]
              | spfunction5[(right2 >>>  8) & 0x3f] | spfunction7[right2 & 0x3f]);
      }
      temp = left; left = right; right = temp; //unreverse left and right
    } //for either 1 or 3 iterations

//move then each one bit to the right
    left = ((left >>> 1) | (left << 31)); 
    right = ((right >>> 1) | (right << 31));

//now perform IP-1, which is IP in the opposite direction
    temp = ((left >>> 1) ^ right) & 0x55555555; right ^= temp; left ^= (temp << 1);
    temp = ((right >>> 8) ^ left) & 0x00ff00ff; left ^= temp; right ^= (temp << 8);
    temp = ((right >>> 2) ^ left) & 0x33333333; left ^= temp; right ^= (temp << 2);
    temp = ((left >>> 16) ^ right) & 0x0000ffff; right ^= temp; left ^= (temp << 16);
    temp = ((left >>> 4) ^ right) & 0x0f0f0f0f; right ^= temp; left ^= (temp << 4);

//for Cipher Block Chaining mode, xor the message with the previous result
    if (mode == 1) {if (encrypt) {cbcleft = left; cbcright = right;} else {left ^= cbcleft2; right ^= cbcright2;}}
    tempresult += String.fromCharCode ((left>>>24), ((left>>>16) & 0xff), ((left>>>8) & 0xff), (left & 0xff), (right>>>24), ((right>>>16) & 0xff), ((right>>>8) & 0xff), (right & 0xff));

chunk += 8;
    if (chunk == 512) {result += tempresult; tempresult = ""; chunk = 0;}
  } //for every 8 characters, or 64 bits in the message

//return the result as an array
  return result + tempresult;
} //end of des

//des_createKeys
//this takes as input a 64 bit key (even though only 56 bits are used)
//as an array of 2 integers, and returns 16 48 bit keys
function des_createKeys (key) {
  //declaring this locally speeds things up a bit
  pc2bytes0  = new Array (0,0x4,0x20000000,0x20000004,0x10000,0x10004,0x20010000,0x20010004,0x200,0x204,0x20000200,0x20000204,0x10200,0x10204,0x20010200,0x20010204);
  pc2bytes1  = new Array (0,0x1,0x100000,0x100001,0x4000000,0x4000001,0x4100000,0x4100001,0x100,0x101,0x100100,0x100101,0x4000100,0x4000101,0x4100100,0x4100101);
  pc2bytes2  = new Array (0,0x8,0x800,0x808,0x1000000,0x1000008,0x1000800,0x1000808,0,0x8,0x800,0x808,0x1000000,0x1000008,0x1000800,0x1000808);
  pc2bytes3  = new Array (0,0x200000,0x8000000,0x8200000,0x2000,0x202000,0x8002000,0x8202000,0x20000,0x220000,0x8020000,0x8220000,0x22000,0x222000,0x8022000,0x8222000);
  pc2bytes4  = new Array (0,0x40000,0x10,0x40010,0,0x40000,0x10,0x40010,0x1000,0x41000,0x1010,0x41010,0x1000,0x41000,0x1010,0x41010);
  pc2bytes5  = new Array (0,0x400,0x20,0x420,0,0x400,0x20,0x420,0x2000000,0x2000400,0x2000020,0x2000420,0x2000000,0x2000400,0x2000020,0x2000420);
  pc2bytes6  = new Array (0,0x10000000,0x80000,0x10080000,0x2,0x10000002,0x80002,0x10080002,0,0x10000000,0x80000,0x10080000,0x2,0x10000002,0x80002,0x10080002);
  pc2bytes7  = new Array (0,0x10000,0x800,0x10800,0x20000000,0x20010000,0x20000800,0x20010800,0x20000,0x30000,0x20800,0x30800,0x20020000,0x20030000,0x20020800,0x20030800);
  pc2bytes8  = new Array (0,0x40000,0,0x40000,0x2,0x40002,0x2,0x40002,0x2000000,0x2040000,0x2000000,0x2040000,0x2000002,0x2040002,0x2000002,0x2040002);
  pc2bytes9  = new Array (0,0x10000000,0x8,0x10000008,0,0x10000000,0x8,0x10000008,0x400,0x10000400,0x408,0x10000408,0x400,0x10000400,0x408,0x10000408);
  pc2bytes10 = new Array (0,0x20,0,0x20,0x100000,0x100020,0x100000,0x100020,0x2000,0x2020,0x2000,0x2020,0x102000,0x102020,0x102000,0x102020);
  pc2bytes11 = new Array (0,0x1000000,0x200,0x1000200,0x200000,0x1200000,0x200200,0x1200200,0x4000000,0x5000000,0x4000200,0x5000200,0x4200000,0x5200000,0x4200200,0x5200200);
  pc2bytes12 = new Array (0,0x1000,0x8000000,0x8001000,0x80000,0x81000,0x8080000,0x8081000,0x10,0x1010,0x8000010,0x8001010,0x80010,0x81010,0x8080010,0x8081010);
  pc2bytes13 = new Array (0,0x4,0x100,0x104,0,0x4,0x100,0x104,0x1,0x5,0x101,0x105,0x1,0x5,0x101,0x105);

//how many iterations (1 for des, 3 for triple des)
  var iterations = key.length >= 24 ? 3 : 1;
  //stores the return keys
  var keys = new Array (32 * iterations);
  //now define the left shifts which need to be done
  var shifts = new Array (0, 0, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 0);
  //other variables
  var lefttemp, righttemp, m=0, n=0, temp;

for (var j=0; j<iterations; j++) { //either 1 or 3 iterations
    left = (key.charCodeAt(m++) << 24) | (key.charCodeAt(m++) << 16) | (key.charCodeAt(m++) << 8) | key.charCodeAt(m++);
    right = (key.charCodeAt(m++) << 24) | (key.charCodeAt(m++) << 16) | (key.charCodeAt(m++) << 8) | key.charCodeAt(m++);

temp = ((left >>> 4) ^ right) & 0x0f0f0f0f; right ^= temp; left ^= (temp << 4);
    temp = ((right >>> -16) ^ left) & 0x0000ffff; left ^= temp; right ^= (temp << -16);
    temp = ((left >>> 2) ^ right) & 0x33333333; right ^= temp; left ^= (temp << 2);
    temp = ((right >>> -16) ^ left) & 0x0000ffff; left ^= temp; right ^= (temp << -16);
    temp = ((left >>> 1) ^ right) & 0x55555555; right ^= temp; left ^= (temp << 1);
    temp = ((right >>> 8) ^ left) & 0x00ff00ff; left ^= temp; right ^= (temp << 8);
    temp = ((left >>> 1) ^ right) & 0x55555555; right ^= temp; left ^= (temp << 1);

//the right side needs to be shifted and to get the last four bits of the left side
    temp = (left << 8) | ((right >>> 20) & 0x000000f0);
    //left needs to be put upside down
    left = (right << 24) | ((right << 8) & 0xff0000) | ((right >>> 8) & 0xff00) | ((right >>> 24) & 0xf0);
    right = temp;

//now go through and perform these shifts on the left and right keys
    for (i=0; i < shifts.length; i++) {
      //shift the keys either one or two bits to the left
      if (shifts[i]) {left = (left << 2) | (left >>> 26); right = (right << 2) | (right >>> 26);}
      else {left = (left << 1) | (left >>> 27); right = (right << 1) | (right >>> 27);}
      left &= 0xfffffff0; right &= 0xfffffff0;

//now apply PC-2, in such a way that E is easier when encrypting or decrypting
      //this conversion will look like PC-2 except only the last 6 bits of each byte are used
      //rather than 48 consecutive bits and the order of lines will be according to 
      //how the S selection functions will be applied: S2, S4, S6, S8, S1, S3, S5, S7
      lefttemp = pc2bytes0[left >>> 28] | pc2bytes1[(left >>> 24) & 0xf]
              | pc2bytes2[(left >>> 20) & 0xf] | pc2bytes3[(left >>> 16) & 0xf]
              | pc2bytes4[(left >>> 12) & 0xf] | pc2bytes5[(left >>> 8) & 0xf]
              | pc2bytes6[(left >>> 4) & 0xf];
      righttemp = pc2bytes7[right >>> 28] | pc2bytes8[(right >>> 24) & 0xf]
                | pc2bytes9[(right >>> 20) & 0xf] | pc2bytes10[(right >>> 16) & 0xf]
                | pc2bytes11[(right >>> 12) & 0xf] | pc2bytes12[(right >>> 8) & 0xf]
                | pc2bytes13[(right >>> 4) & 0xf];
      temp = ((righttemp >>> 16) ^ lefttemp) & 0x0000ffff; 
      keys[n++] = lefttemp ^ temp; keys[n++] = righttemp ^ (temp << 16);
    }
  } //for each iterations
  //return the keys we've created
  return keys;
} //end of des_createKeys

////////////////////////////// TEST //////////////////////////////
//printHexArray
function printHex (s) {
  var r = "0x";
  var hexes = new Array ("0","1","2","3","4","5","6","7","8","9","a","b","c","d","e","f");
  for (var i=0; i<s.length; i++) {r += hexes [s.charCodeAt(i) >> 4] + hexes [s.charCodeAt(i) & 0xf];}
  return r;
}

var key = "this is a 24 byte key !!";
var message = "This is a test message";
var ciphertext = des (key, message, 1, 0);
document.writeln ("DES Test: " + printHex (ciphertext));

Posted from http://www.shopable.co.uk/des.html with permission. Special thanks to Paul Back (DES Explanation)

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