internal static int horst_verify(HashFunctions hs, byte[] pk, byte[] sig, int sigOff, byte[] masks, byte[] m_hash)
{
byte[] buffer = new byte[32 * HASH_BYTES];
uint idx;
int i, j, k;
int sigOffset = sigOff + 64 * HASH_BYTES;
for (i = 0; i < HORST_K; i++)
{
idx = (uint)((m_hash[2 * i] & 0xff) + ((m_hash[2 * i + 1] & 0xff) << 8));
if ((idx & 1) == 0)
{
hs.hash_n_n(buffer, 0, sig, sigOffset);
for (k = 0; k < HASH_BYTES; k++)
{
buffer[HASH_BYTES + k] = sig[sigOffset + HORST_SKBYTES + k];
}
}
else
{
hs.hash_n_n(buffer, HASH_BYTES, sig, sigOffset);
for (k = 0; k < HASH_BYTES; k++)
{
buffer[k] = sig[sigOffset + HORST_SKBYTES + k];
}
}
sigOffset += HORST_SKBYTES + HASH_BYTES;
for (j = 1; j < HORST_LOGT - 6; j++)
{
idx = idx >> 1; // parent node
if ((idx & 1) == 0)
{
hs.hash_2n_n_mask(buffer, 0, buffer, 0, masks, 2 * (j - 1) * HASH_BYTES);
for (k = 0; k < HASH_BYTES; k++)
{
buffer[HASH_BYTES + k] = sig[sigOffset + k];
}
}
else
{
hs.hash_2n_n_mask(buffer, HASH_BYTES, buffer, 0, masks, 2 * (j - 1) * HASH_BYTES);
for (k = 0; k < HASH_BYTES; k++)
{
buffer[k] = sig[sigOffset + k];
}
}
sigOffset += HASH_BYTES;
}
idx = idx >> 1; // parent node
hs.hash_2n_n_mask(buffer, 0, buffer, 0, masks, 2 * (HORST_LOGT - 7) * HASH_BYTES);
for (k = 0; k < HASH_BYTES; k++)
{
if (sig[sigOff + idx * HASH_BYTES + k] != buffer[k])
{
for (k = 0; k < HASH_BYTES; k++)
{
pk[k] = 0;
}
return(-1);
}
}
}
// Compute root from level10
for (j = 0; j < 32; j++)
{
hs.hash_2n_n_mask(buffer, j * HASH_BYTES, sig, sigOff + 2 * j * HASH_BYTES, masks, 2 * (HORST_LOGT - 6) * HASH_BYTES);
}
// Hash from level 11 to 12
for (j = 0; j < 16; j++)
{
hs.hash_2n_n_mask(buffer, j * HASH_BYTES, buffer, 2 * j * HASH_BYTES, masks, 2 * (HORST_LOGT - 5) * HASH_BYTES);
}
// Hash from level 12 to 13
for (j = 0; j < 8; j++)
{
hs.hash_2n_n_mask(buffer, j * HASH_BYTES, buffer, 2 * j * HASH_BYTES, masks, 2 * (HORST_LOGT - 4) * HASH_BYTES);
}
// Hash from level 13 to 14
for (j = 0; j < 4; j++)
{
hs.hash_2n_n_mask(buffer, j * HASH_BYTES, buffer, 2 * j * HASH_BYTES, masks, 2 * (HORST_LOGT - 3) * HASH_BYTES);
}
// Hash from level 14 to 15
for (j = 0; j < 2; j++)
{
hs.hash_2n_n_mask(buffer, j * HASH_BYTES, buffer, 2 * j * HASH_BYTES, masks, 2 * (HORST_LOGT - 2) * HASH_BYTES);
}
// Hash from level 15 to 16
hs.hash_2n_n_mask(pk, 0, buffer, 0, masks, 2 * (HORST_LOGT - 1) * HASH_BYTES);
return(0);
}
internal static int horst_sign(HashFunctions hs,
byte[] sig, int sigOff, byte[] pk,
byte[] seed,
byte[] masks,
byte[] m_hash)
{
byte[] sk = new byte[HORST_T * HORST_SKBYTES];
uint idx;
int i, j, k;
int sigpos = sigOff;
byte[] tree = new byte[(2 * HORST_T - 1) * HASH_BYTES]; /* replace by something more memory-efficient? */
expand_seed(sk, seed);
// Build the whole tree and save it
// Generate pk leaves
for (i = 0; i < HORST_T; i++)
{
hs.hash_n_n(tree, (HORST_T - 1 + i) * HASH_BYTES, sk, i * HORST_SKBYTES);
}
long offset_in, offset_out;
for (i = 0; i < HORST_LOGT; i++)
{
offset_in = (1 << (HORST_LOGT - i)) - 1;
offset_out = (1 << (HORST_LOGT - i - 1)) - 1;
for (j = 0; j < (1 << (HORST_LOGT - i - 1)); j++)
{
hs.hash_2n_n_mask(tree, (int)((offset_out + j) * HASH_BYTES), tree, (int)((offset_in + 2 * j) * HASH_BYTES), masks, 2 * i * HASH_BYTES);
}
}
// First write 64 hashes from level 10 to the signature
for (j = 63 * HASH_BYTES; j < 127 * HASH_BYTES; j++)
{
sig[sigpos++] = tree[j];
}
// Signature consists of HORST_K parts; each part of secret key and HORST_LOGT-4 auth-path hashes
for (i = 0; i < HORST_K; i++)
{
idx = (uint)((m_hash[2 * i] & 0xff) + ((m_hash[2 * i + 1] & 0xff) << 8));
for (k = 0; k < HORST_SKBYTES; k++)
{
sig[sigpos++] = sk[idx * HORST_SKBYTES + k];
}
idx += (uint)(HORST_T - 1);
for (j = 0; j < HORST_LOGT - 6; j++)
{
idx = ((idx & 1) != 0) ? idx + 1 : idx - 1; // neighbor node
for (k = 0; k < HASH_BYTES; k++)
{
sig[sigpos++] = tree[idx * HASH_BYTES + k];
}
idx = (idx - 1) / 2; // parent node
}
}
for (i = 0; i < HASH_BYTES; i++)
{
pk[i] = tree[i];
}
return(HORST_SIGBYTES);
}
