function identification() {
	var id = document.getElementById("login").value;
	var pwd = document.getElementById("pwd").value;
	return !sendData('POST','script/ova-session.php','id='+id+'&'+'pwd='+sha1Hash(pwd));
}

function getHTTPObject()
{
  var xmlhttp = false;

  /* Compilation conditionnelle d'IE */
  /*@cc_on
  @if (@_jscript_version >= 5)
     try
     {
        xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
     }
     catch (e)
     {
        try
        {
           xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
        catch (E)
        {
           xmlhttp = false;
        }
     }
  @else
     xmlhttp = false;
  @end @*/

  /* on essaie de créer l'objet si ce n'est pas déjà fait */
  if (!xmlhttp && typeof XMLHttpRequest != 'undefined')
  {
     try
     {
        xmlhttp = new XMLHttpRequest();
     }
     catch (e)
     {
        xmlhttp = false;
     }
  }

  if (xmlhttp)
  {
     /* on définit ce qui doit se passer quand la page répondra */
     xmlhttp.onreadystatechange=function()
     {
        if (xmlhttp.readyState == 4) /* 4 : état "complete" */
        {
           if (xmlhttp.status == 200) /* 200 : code HTTP pour OK */
           {
			switch(xmlhttp.responseText)
			{
				case '':
				  var p = document.createElement('p');
				  p.style.color = 'red';
				  p.style.fontWeight = 'bold';
				  p.appendChild(document.createTextNode("Vos identifiants sont inconnus. Veuillez les ressaisir."));
				  document.getElementById('contenu-centre').insertBefore(p,document.getElementById('ova-session'));
				  break;
				case 'charge_OK':
				  break;
				default:
			      document.getElementById('contenu-centre').innerHTML = xmlhttp.responseText;
			  	  initialize_form();
		 	}
           }
     	}
  	}
  }
  return xmlhttp;
}

/**
  * Envoie des données à l'aide d'XmlHttpRequest?
  * @param string methode d'envoi ['GET'|'POST']
  * @param string url
  * @param string données à envoyer sous la forme var1=value1&var2=value2...
  */
 function sendData(method, url, data)
 {
    var xmlhttp = getHTTPObject();

    if (!xmlhttp)
    {
        return false;
    }

    if(method == "GET")
     {
     if(data == 'null')
     {
            xmlhttp.open("GET", url, true); //ouverture asynchrone
     }
     else
     {
            xmlhttp.open("GET", url+"?"+data, true);
     }
        xmlhttp.send(null);
     }
     else if(method == "POST")
     {
        xmlhttp.open("POST", url, true); //ouverture asynchrone
        xmlhttp.setRequestHeader('Content-Type','application/x-www-form-urlencoded;');
		xmlhttp.send(data);
     }
    return true;
 }


/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
/*  SHA-1 implementation in JavaScript (c) Chris Veness 2002-2009                                 */
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */

function sha1Hash(msg)
{
    // constants [§4.2.1]
    var K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];


    // PREPROCESSING 
 
    msg += String.fromCharCode(0x80); // add trailing '1' bit (+ 0's padding) to string [§5.1.1]

    // convert string msg into 512-bit/16-integer blocks arrays of ints [§5.2.1]
    var l = msg.length/4 + 2;  // length (in 32-bit integers) of msg + ‘1’ + appended length
	var N = Math.ceil(l/16);   // number of 16-integer-blocks required to hold 'l' ints
	var M = new Array(N);
    for (var i=0; i<N; i++) {
        M[i] = new Array(16);
        for (var j=0; j<16; j++) {  // encode 4 chars per integer, big-endian encoding
            M[i][j] = (msg.charCodeAt(i*64+j*4)<<24) | (msg.charCodeAt(i*64+j*4+1)<<16) | 
                      (msg.charCodeAt(i*64+j*4+2)<<8) | (msg.charCodeAt(i*64+j*4+3));
        }
    }
    // add length (in bits) into final pair of 32-bit integers (big-endian) [5.1.1]
    // note: most significant word would be (len-1)*8 >>> 32, but since JS converts
    // bitwise-op args to 32 bits, we need to simulate this by arithmetic operators
    M[N-1][14] = ((msg.length-1)*8) / Math.pow(2, 32); M[N-1][14] = Math.floor(M[N-1][14])
    M[N-1][15] = ((msg.length-1)*8) & 0xffffffff;

    // set initial hash value [§5.3.1]
    var H0 = 0x67452301;
    var H1 = 0xefcdab89;
    var H2 = 0x98badcfe;
    var H3 = 0x10325476;
    var H4 = 0xc3d2e1f0;

    // HASH COMPUTATION [§6.1.2]

    var W = new Array(80); var a, b, c, d, e;
    for (var i=0; i<N; i++) {

        // 1 - prepare message schedule 'W'
        for (var t=0;  t<16; t++) W[t] = M[i][t];
        for (var t=16; t<80; t++) W[t] = ROTL(W[t-3] ^ W[t-8] ^ W[t-14] ^ W[t-16], 1);

        // 2 - initialise five working variables a, b, c, d, e with previous hash value
        a = H0; b = H1; c = H2; d = H3; e = H4;

        // 3 - main loop
        for (var t=0; t<80; t++) {
            var s = Math.floor(t/20); // seq for blocks of 'f' functions and 'K' constants
            var T = (ROTL(a,5) + f(s,b,c,d) + e + K[s] + W[t]) & 0xffffffff;
            e = d;
            d = c;
            c = ROTL(b, 30);
            b = a;
            a = T;
        }

        // 4 - compute the new intermediate hash value
        H0 = (H0+a) & 0xffffffff;  // note 'addition modulo 2^32'
        H1 = (H1+b) & 0xffffffff; 
        H2 = (H2+c) & 0xffffffff; 
        H3 = (H3+d) & 0xffffffff; 
        H4 = (H4+e) & 0xffffffff;
    }

    return H0.toHexStr() + H1.toHexStr() + H2.toHexStr() + H3.toHexStr() + H4.toHexStr();
}

//
// function 'f' [§4.1.1]
//
function f(s, x, y, z) 
{
    switch (s) {
    case 0: return (x & y) ^ (~x & z);           // Ch()
    case 1: return x ^ y ^ z;                    // Parity()
    case 2: return (x & y) ^ (x & z) ^ (y & z);  // Maj()
    case 3: return x ^ y ^ z;                    // Parity()
    }
}

//
// rotate left (circular left shift) value x by n positions [§3.2.5]
//
function ROTL(x, n)
{
    return (x<<n) | (x>>>(32-n));
}

//
// extend Number class with a tailored hex-string method 
//   (note toString(16) is implementation-dependant, and 
//   in IE returns signed numbers when used on full words)
//
Number.prototype.toHexStr = function()
{
    var s="", v;
    for (var i=7; i>=0; i--) { v = (this>>>(i*4)) & 0xf; s += v.toString(16); }
    return s;
}
/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */