Exemple complet d'algorithme de chiffrement SHA-1 implémenté dans les compétences JavaScript_javascript

/**
*
* Secure Hash Algorithm (SHA1)
* http://www.webtoolkit.info/
*
**/
function SHA1 (msg) {
  function rotate_left(n,s) {
    var t4 = ( n<<s ) | (n>>>(32-s));
    return t4;
  };
  function lsb_hex(val) {
    var str="";
    var i;
    var vh;
    var vl;
    for( i=0; i<=6; i+=2 ) {
      vh = (val>>>(i*4+4))&0x0f;
      vl = (val>>>(i*4))&0x0f;
      str += vh.toString(16) + vl.toString(16);
    }
    return str;
  };
  function cvt_hex(val) {
    var str="";
    var i;
    var v;
    for( i=7; i>=0; i-- ) {
      v = (val>>>(i*4))&0x0f;
      str += v.toString(16);
    }
    return str;
  };
  function Utf8Encode(string) {
    string = string.replace(/\r\n/g,"\n");
    var utftext = "";
    for (var n = 0; n < string.length; n++) {
      var c = string.charCodeAt(n);
      if (c < 128) {
        utftext += String.fromCharCode(c);
      }
      else if((c > 127) && (c < 2048)) {
        utftext += String.fromCharCode((c >> 6) | 192);
        utftext += String.fromCharCode((c & 63) | 128);
      }
      else {
        utftext += String.fromCharCode((c >> 12) | 224);
        utftext += String.fromCharCode(((c >> 6) & 63) | 128);
        utftext += String.fromCharCode((c & 63) | 128);
      }
    }
    return utftext;
  };
  var blockstart;
  var i, j;
  var W = new Array(80);
  var H0 = 0x67452301;
  var H1 = 0xEFCDAB89;
  var H2 = 0x98BADCFE;
  var H3 = 0x10325476;
  var H4 = 0xC3D2E1F0;
  var A, B, C, D, E;
  var temp;
  msg = Utf8Encode(msg);
  var msg_len = msg.length;
  var word_array = new Array();
  for( i=0; i<msg_len-3; i+=4 ) {
    j = msg.charCodeAt(i)<<24 | msg.charCodeAt(i+1)<<16 |
    msg.charCodeAt(i+2)<<8 | msg.charCodeAt(i+3);
    word_array.push( j );
  }
  switch( msg_len % 4 ) {
    case 0:
      i = 0x080000000;
    break;
    case 1:
      i = msg.charCodeAt(msg_len-1)<<24 | 0x0800000;
    break;
    case 2:
      i = msg.charCodeAt(msg_len-2)<<24 | msg.charCodeAt(msg_len-1)<<16 | 0x08000;
    break;
    case 3:
      i = msg.charCodeAt(msg_len-3)<<24 | msg.charCodeAt(msg_len-2)<<16 | msg.charCodeAt(msg_len-1)<<8  | 0x80;
    break;
  }
  word_array.push( i );
  while( (word_array.length % 16) != 14 ) word_array.push( 0 );
  word_array.push( msg_len>>>29 );
  word_array.push( (msg_len<<3)&0x0ffffffff );
  for ( blockstart=0; blockstart<word_array.length; blockstart+=16 ) {
    for( i=0; i<16; i++ ) W[i] = word_array[blockstart+i];
    for( i=16; i<=79; i++ ) W[i] = rotate_left(W[i-3] ^ W[i-8] ^ W[i-14] ^ W[i-16], 1);
    A = H0;
    B = H1;
    C = H2;
    D = H3;
    E = H4;
    for( i= 0; i<=19; i++ ) {
      temp = (rotate_left(A,5) + ((B&C) | (~B&D)) + E + W[i] + 0x5A827999) & 0x0ffffffff;
      E = D;
      D = C;
      C = rotate_left(B,30);
      B = A;
      A = temp;
    }
    for( i=20; i<=39; i++ ) {
      temp = (rotate_left(A,5) + (B ^ C ^ D) + E + W[i] + 0x6ED9EBA1) & 0x0ffffffff;
      E = D;
      D = C;
      C = rotate_left(B,30);
      B = A;
      A = temp;
    }
    for( i=40; i<=59; i++ ) {
      temp = (rotate_left(A,5) + ((B&C) | (B&D) | (C&D)) + E + W[i] + 0x8F1BBCDC) & 0x0ffffffff;
      E = D;
      D = C;
      C = rotate_left(B,30);
      B = A;
      A = temp;
    }
    for( i=60; i<=79; i++ ) {
      temp = (rotate_left(A,5) + (B ^ C ^ D) + E + W[i] + 0xCA62C1D6) & 0x0ffffffff;
      E = D;
      D = C;
      C = rotate_left(B,30);
      B = A;
      A = temp;
    }
    H0 = (H0 + A) & 0x0ffffffff;
    H1 = (H1 + B) & 0x0ffffffff;
    H2 = (H2 + C) & 0x0ffffffff;
    H3 = (H3 + D) & 0x0ffffffff;
    H4 = (H4 + E) & 0x0ffffffff;
  }
  var temp = cvt_hex(H0) + cvt_hex(H1) + cvt_hex(H2) + cvt_hex(H3) + cvt_hex(H4);
  return temp.toLowerCase();
}