// Uses supplied hash algorithm
static byte[] derive(
char[] chars, byte[] salt, int ic, int n, int type, String hashAlgo, int blockLength) {
// Add in trailing NULL terminator. Special case:
// no terminator if password is "\0".
int length = chars.length * 2;
if (length == 2 && chars[0] == 0) {
chars = new char[0];
length = 0;
} else {
length += 2;
}
byte[] passwd = new byte[length];
for (int i = 0, j = 0; i < chars.length; i++, j += 2) {
passwd[j] = (byte) ((chars[i] >>> 8) & 0xFF);
passwd[j + 1] = (byte) (chars[i] & 0xFF);
}
byte[] key = new byte[n];
try {
MessageDigest sha = MessageDigest.getInstance(hashAlgo);
int v = blockLength;
int u = sha.getDigestLength();
int c = roundup(n, u) / u;
byte[] D = new byte[v];
int s = roundup(salt.length, v);
int p = roundup(passwd.length, v);
byte[] I = new byte[s + p];
Arrays.fill(D, (byte) type);
concat(salt, I, 0, s);
concat(passwd, I, s, p);
byte[] Ai;
byte[] B = new byte[v];
byte[] tmp = new byte[v];
int i = 0;
for (; ; i++, n -= u) {
sha.update(D);
sha.update(I);
Ai = sha.digest();
for (int r = 1; r < ic; r++) Ai = sha.digest(Ai);
System.arraycopy(Ai, 0, key, u * i, Math.min(n, u));
if (i + 1 == c) break;
concat(Ai, B, 0, B.length);
BigInteger B1;
B1 = new BigInteger(1, B).add(BigInteger.ONE);
for (int j = 0; j < I.length; j += v) {
BigInteger Ij;
int trunc;
if (tmp.length != v) tmp = new byte[v];
System.arraycopy(I, j, tmp, 0, v);
Ij = new BigInteger(1, tmp);
Ij = Ij.add(B1);
tmp = Ij.toByteArray();
trunc = tmp.length - v;
if (trunc >= 0) {
System.arraycopy(tmp, trunc, I, j, v);
} else if (trunc < 0) {
Arrays.fill(I, j, j + (-trunc), (byte) 0);
System.arraycopy(tmp, 0, I, j + (-trunc), tmp.length);
}
}
}
} catch (Exception e) {
throw new RuntimeException("internal error: " + e);
}
return key;
}
/** Standard constructor, creates a new HmacSHA1 instance. */
public HmacSHA1() throws NoSuchAlgorithmException {
this.hmac = new HmacCore(MessageDigest.getInstance("SHA1"), SHA1_BLOCK_LENGTH);
}