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srp.Session = function(login, password) {
// Variables session will be used in the SRP protocol
var Nstr = "eeaf0ab9adb38dd69c33f80afa8fc5e86072618775ff3c0b9ea2314c9c256576d674df7496ea81d3383b4813d692c6e0e0d5d8e250b98be48e495c1d6089dad15dc7d7b46154d6b6ce8ef4ad69b15d4982559b297bcf1885c529f566660e57ec68edbc3c05726cc02fd4cbf4976eaa9afd5138fe8376435b9fc61d2fc0eb06e3";
var N = new BigInteger(Nstr, 16);
var g = new BigInteger("2");
var k = new BigInteger("bf66c44a428916cad64aa7c679f3fd897ad4c375e9bbb4cbf2f5de241d618ef0", 16);
var rng = new SecureRandom();
// var a = new BigInteger(32, rng);
var a = new BigInteger("d498c3d024ec17689b5320e33fc349a3f3f91320384155b3043fa410c90eab71", 16);
var A = g.modPow(a, N);
while(A.mod(N) == 0)
{
a = new BigInteger(32, rng);
A = g.modPow(a, N);
}
var Astr = A.toString(16);
var S = null;
var K = null;
var M = null;
var M2 = null;
var authenticated = false;
var I = login;
var pass = password;
// *** Accessor methods ***
// allows setting the random number A for testing
this.calculateAndSetA = function(_a) {
a = new BigInteger(_a, 16);
A = g.modPow(a, N);
Astr = A.toString(16);
return Astr;
};
this.signup = function() {
var salt = this.getSalt();
return {
login: this.getI(),
password_salt: salt,
password_verifier: this.getV(salt).toString(16)
};
};
this.handshake = function() {
return {
login: this.getI(),
A: this.getAstr()
};
};
this.getAstr = function() {
return Astr;
}
// Returns the user's identity
this.getI = function() {
I = I || document.getElementById("srp_username").value;
return I;
};
// Returns the user's identity
this.getPass = function() {
pass = pass || document.getElementById("srp_password").value;
return pass;
};
// some 16 byte random number
this.getSalt = function() {
return new BigInteger(64, rng).toString(16);
}
// Returns the BigInteger, g
this.getg = function() {
return g;
};
// Returns the BigInteger, N
this.getN = function() {
return N;
};
// Calculates the X value and return it as a BigInteger
this.calcX = function(salt) {
var inner = salt + SHA256(this.getI() + ":" + this.getPass())
return new BigInteger(SHA256(hex2a(inner)), 16);
};
this.getV = function(salt)
{
return this.getg().modPow(this.calcX(salt), this.getN());
}
// Calculate S, M, and M2
// This is the client side of the SRP specification
this.calculations = function(salt, ephemeral)
{
//S -> C: s | B
var B = new BigInteger(ephemeral, 16);
var Bstr = ephemeral;
// u = H(A,B)
var u = new BigInteger(SHA256(hex2a(Astr + Bstr)), 16);
// x = H(s, H(I:p))
var x = this.calcX(salt);
//S = (B - kg^x) ^ (a + ux)
var kgx = k.multiply(g.modPow(x, N));
var aux = a.add(u.multiply(x));
S = B.subtract(kgx).modPow(aux, N);
K = SHA256(hex2a(S.toString(16)));
this.calcM(salt, A.toString(16), B.toString(16));
};
// M = H(H(N) xor H(g), H(I), s, A, B, K)
this.calcM = function(salt, Astr, Bstr) {
var hashN = SHA256(hex2a(N.toString(16)))
var hashG = SHA256(hex2a(g.toString(16)))
var hexString = hexXor(hashN, hashG);
hexString += SHA256(I);
hexString += salt;
hexString += Astr;
hexString += Bstr;
hexString += K
M = SHA256(hex2a(hexString));
//M2 = H(A, M, K)
M2 = SHA256(hex2a(Astr + M + K));
};
this.getM = function() {
return M;
}
this.validate = function(serverM2) {
authenticated = (serverM2 && serverM2 == M2)
return authenticated;
}
// If someone wants to use the session key for encrypting traffic, they can
// access the key with this function.
this.key = function()
{
if(K) {
return K;
} else {
this.onError("User has not been authenticated.");
}
};
// Encrypt plaintext using slowAES
this.encrypt = function(plaintext)
{
var key = cryptoHelpers.toNumbers(session.key());
var byteMessage = cryptoHelpers.convertStringToByteArray(plaintext);
var iv = new Array(16);
rng.nextBytes(iv);
var paddedByteMessage = slowAES.getPaddedBlock(byteMessage, 0, byteMessage.length, slowAES.modeOfOperation.CFB);
var ciphertext = slowAES.encrypt(paddedByteMessage, slowAES.modeOfOperation.CFB, key, key.length, iv).cipher;
var retstring = cryptoHelpers.base64.encode(iv.concat(ciphertext));
while(retstring.indexOf("+",0) > -1)
retstring = retstring.replace("+", "_");
return retstring;
};
function hex2a(hex) {
var str = '';
for (var i = 0; i < hex.length; i += 2)
str += String.fromCharCode(parseInt(hex.substr(i, 2), 16));
return str;
}
function hexXor(a, b) {
var str = '';
for (var i = 0; i < a.length; i += 2) {
var xor = parseInt(a.substr(i, 2), 16) ^ parseInt(b.substr(i, 2), 16)
xor = xor.toString(16);
str += (xor.length == 1) ? ("0" + xor) : xor
}
return str;
}
};
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