/**
* Key Derivation Function 2 (KDF2) from the IEEE P1363a draft standard. It generates a secret key
* of length oLen bits from shared secret Z and key derivation parameter P.
*/
public static int[] KDF2(int[] Z, int oLen, int[] P) {
// Note:
// oLen cannot be > hbits * (2^32-1) bits, because the size of an
// int is 32 bits
int[] K = new int[0];
int[] CB = new int[1];
int cThreshold = (oLen / 160);
if (oLen % 160 != 0) cThreshold++;
try {
MessageDigest sha = MessageDigest.getInstance("SHA");
// sha.update(data);
// byte[] hash = sha.digest(data);
for (byte i = 1; i <= cThreshold; i++) {
CB[0] = i;
sha.update(Utils.toByteArray(Utils.concatenate(Z, CB, P)));
K = Utils.concatenate(K, Utils.revIntArray(Utils.toIntArray(sha.digest())));
// K = Utils.concatenate(K, Utils.toIntArray(sha.digest()));
sha.reset(); // not needed after diget()
}
} catch (NoSuchAlgorithmException e) {
}
// return Utils.resize (Utils.revIntArray(K), oLen);
return Utils.resize(K, oLen);
}
/**
* MAC1 as described in the IEEE P1363 standard. It computes a HMAC message authentication code
* tag from secret key KB and message M.
*/
public static int[] MAC1(int[] K, int[] M) {
int[] HH = new int[0];
try {
int i;
int[] KK;
MessageDigest sha = MessageDigest.getInstance("SHA");
// SHA1 Blocksize B = 512
if (K.length > (8 * 512)) {
sha.update(Utils.toByteArray(K));
// kkLen = 20 octets, 160 bits
KK = Utils.revIntArray(Utils.toIntArray(sha.digest()));
} else KK = K;
int[] P = new int[512 - KK.length];
for (i = 0; i < P.length; i++) {
P[i] = 0;
}
int[] K0 = Utils.concatenate(KK, P);
int[] iPad = new int[512];
for (i = 0; i < iPad.length; i++) {
iPad[i] = 0x36;
}
int[] oPad = new int[512];
for (i = 0; i < oPad.length; i++) {
oPad[i] = 0x54;
}
sha.reset();
sha.update(Utils.toByteArray(Utils.concatenate(Utils.xor(K0, iPad), M)));
int[] H = Utils.revIntArray(Utils.toIntArray(sha.digest()));
sha.reset();
sha.update(Utils.toByteArray(Utils.concatenate(Utils.xor(K0, oPad), H)));
HH = Utils.revIntArray(Utils.toIntArray(sha.digest()));
} catch (NoSuchAlgorithmException e) {
}
return HH;
}