function checkQ(str){
	correct_answer=str+'_correct';
	if(sha1Hash(document.getElementById(str).value.toLowerCase()) == document.getElementById(correct_answer).value){
		validate1(str);
	}else{
		validate2(str);
	}
	
}
function validate1(qstr) {
	idpic=qstr+'_pic';
	document.getElementById(qstr).style.border = '2px solid #00FF00'; 
	document.getElementById(idpic).src = imageSource[1].src;
}
function validate2(qstr) {
	idpic=qstr+'_pic';
	if(document.getElementById(qstr).value=='') {
		document.getElementById(qstr).style.border = '1px solid #A5ACB2'; 
		document.getElementById(idpic).src = imageSource[2].src;
	}else{
		document.getElementById(qstr).style.border = '2px solid #FF0000'; 
		document.getElementById(idpic).src = imageSource[0].src;
	}
}
function sha1Hash(msg){
	// constants [4.2.1]
	var K = [0x5a827999, 0x6ed9eba1, 0x8f1bbcdc, 0xca62c1d6];

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

	// convert string msg into 512-bit/16-integer blocks arrays of ints [5.2.1]
	var l = Math.ceil(msg.length/4) + 2;  // long enough to contain msg plus 2-word length
	var N = Math.ceil(l/16);// in N 16-int blocks
	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));
		}// note running off the end of msg is ok 'cos bitwise ops on NaN return 0
	}
	// add length (in bits) into final pair of 32-bit integers (big-endian) [5.1.1]
	M[N-1][14] = ((msg.length-1) >>> 30) * 8;
	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);
		case 1: return x ^ y ^ z;
		case 2: return (x & y) ^ (x & z) ^ (y & z);
		case 3: return x ^ y ^ z;
	}
}

//
// 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;
}