1 files changed, 192 insertions, 0 deletions
diff --git a/xmss_wots.c b/xmss_wots.c
new file mode 100644
index 0000000..993e661
--- /dev/null
+++ b/xmss_wots.c
@@ -0,0 +1,192 @@
+/* $OpenBSD: xmss_wots.c,v 1.3 2018/04/10 00:10:49 djm Exp $ */
+/*
+wots.c version 20160722
+Andreas Hülsing
+Joost Rijneveld
+Public domain.
+*/
+
+#include "includes.h"
+#ifdef WITH_XMSS
+
+#include <stdlib.h>
+#ifdef HAVE_STDINT_H
+# include <stdint.h>
+#endif
+#include <limits.h>
+#include "xmss_commons.h"
+#include "xmss_hash.h"
+#include "xmss_wots.h"
+#include "xmss_hash_address.h"
+
+
+/* libm-free version of log2() for wots */
+static inline int
+wots_log2(uint32_t v)
+{
+  int      b;
+
+  for (b = sizeof (v) * CHAR_BIT - 1; b >= 0; b--) {
+    if ((1U << b) & v) {
+      return b;
+    }
+  }
+  return 0;
+}
+
+void
+wots_set_params(wots_params *params, int n, int w)
+{
+  params->n = n;
+  params->w = w;
+  params->log_w = wots_log2(params->w);
+  params->len_1 = (CHAR_BIT * n) / params->log_w;
+  params->len_2 = (wots_log2(params->len_1 * (w - 1)) / params->log_w) + 1;
+  params->len = params->len_1 + params->len_2;
+  params->keysize = params->len * params->n;
+}
+
+/**
+ * Helper method for pseudorandom key generation
+ * Expands an n-byte array into a len*n byte array
+ * this is done using PRF
+ */
+static void expand_seed(unsigned char *outseeds, const unsigned char *inseed, const wots_params *params)
+{
+  uint32_t i = 0;
+  unsigned char ctr[32];
+  for(i = 0; i < params->len; i++){
+    to_byte(ctr, i, 32);
+    prf((outseeds + (i*params->n)), ctr, inseed, params->n);
+  }
+}
+
+/**
+ * Computes the chaining function.
+ * out and in have to be n-byte arrays
+ *
+ * interprets in as start-th value of the chain
+ * addr has to contain the address of the chain
+ */
+static void gen_chain(unsigned char *out, const unsigned char *in, unsigned int start, unsigned int steps, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
+{
+  uint32_t i, j;
+  for (j = 0; j < params->n; j++)
+    out[j] = in[j];
+
+  for (i = start; i < (start+steps) && i < params->w; i++) {
+    setHashADRS(addr, i);
+    hash_f(out, out, pub_seed, addr, params->n);
+  }
+}
+
+/**
+ * base_w algorithm as described in draft.
+ *
+ *
+ */
+static void base_w(int *output, const int out_len, const unsigned char *input, const wots_params *params)
+{
+  int in = 0;
+  int out = 0;
+  uint32_t total = 0;
+  int bits = 0;
+  int consumed = 0;
+
+  for (consumed = 0; consumed < out_len; consumed++) {
+    if (bits == 0) {
+      total = input[in];
+      in++;
+      bits += 8;
+    }
+    bits -= params->log_w;
+    output[out] = (total >> bits) & (params->w - 1);
+    out++;
+  }
+}
+
+void wots_pkgen(unsigned char *pk, const unsigned char *sk, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
+{
+  uint32_t i;
+  expand_seed(pk, sk, params);
+  for (i=0; i < params->len; i++) {
+    setChainADRS(addr, i);
+    gen_chain(pk+i*params->n, pk+i*params->n, 0, params->w-1, params, pub_seed, addr);
+  }
+}
+
+
+int wots_sign(unsigned char *sig, const unsigned char *msg, const unsigned char *sk, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
+{
+  //int basew[params->len];
+  int csum = 0;
+  uint32_t i = 0;
+  int *basew = calloc(params->len, sizeof(int));
+  if (basew == NULL)
+    return -1;
+
+  base_w(basew, params->len_1, msg, params);
+
+  for (i=0; i < params->len_1; i++) {
+    csum += params->w - 1 - basew[i];
+  }
+
+  csum = csum << (8 - ((params->len_2 * params->log_w) % 8));
+
+  int len_2_bytes = ((params->len_2 * params->log_w) + 7) / 8;
+
+  unsigned char csum_bytes[len_2_bytes];
+  to_byte(csum_bytes, csum, len_2_bytes);
+
+  int csum_basew[params->len_2];
+  base_w(csum_basew, params->len_2, csum_bytes, params);
+
+  for (i = 0; i < params->len_2; i++) {
+    basew[params->len_1 + i] = csum_basew[i];
+  }
+
+  expand_seed(sig, sk, params);
+
+  for (i = 0; i < params->len; i++) {
+    setChainADRS(addr, i);
+    gen_chain(sig+i*params->n, sig+i*params->n, 0, basew[i], params, pub_seed, addr);
+  }
+  free(basew);
+  return 0;
+}
+
+int wots_pkFromSig(unsigned char *pk, const unsigned char *sig, const unsigned char *msg, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
+{
+  int csum = 0;
+  uint32_t i = 0;
+  int *basew = calloc(params->len, sizeof(int));
+  if (basew == NULL)
+    return -1;
+
+  base_w(basew, params->len_1, msg, params);
+
+  for (i=0; i < params->len_1; i++) {
+    csum += params->w - 1 - basew[i];
+  }
+
+  csum = csum << (8 - ((params->len_2 * params->log_w) % 8));
+
+  int len_2_bytes = ((params->len_2 * params->log_w) + 7) / 8;
+
+  unsigned char csum_bytes[len_2_bytes];
+  to_byte(csum_bytes, csum, len_2_bytes);
+
+  int csum_basew[params->len_2];
+  base_w(csum_basew, params->len_2, csum_bytes, params);
+
+  for (i = 0; i < params->len_2; i++) {
+    basew[params->len_1 + i] = csum_basew[i];
+  }
+  for (i=0; i < params->len; i++) {
+    setChainADRS(addr, i);
+    gen_chain(pk+i*params->n, sig+i*params->n, basew[i], params->w-1-basew[i], params, pub_seed, addr);
+  }
+  free(basew);
+  return 0;
+}
+#endif /* WITH_XMSS */