1 files changed, 101 insertions, 0 deletions
diff --git a/src/crypto/spx/address.c b/src/crypto/spx/address.c
new file mode 100644
index 00000000..13ca2f0c
--- /dev/null
+++ b/src/crypto/spx/address.c
@@ -0,0 +1,101 @@
+/* Copyright (c) 2023, Google LLC
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+ * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+ * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+ * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
+
+#include <openssl/base.h>
+
+#include <string.h>
+
+#include "../internal.h"
+#include "./address.h"
+#include "./spx_util.h"
+
+
+// Offsets of various fields in the address structure for SPHINCS+-SHA2-128s.
+
+// The byte used to specify the Merkle tree layer.
+#define SPX_OFFSET_LAYER 0
+
+// The start of the 8 byte field used to specify the tree.
+#define SPX_OFFSET_TREE 1
+
+// The byte used to specify the hash type (reason).
+#define SPX_OFFSET_TYPE 9
+
+// The high byte used to specify the key pair (which one-time signature).
+#define SPX_OFFSET_KP_ADDR2 12
+
+// The low byte used to specific the key pair.
+#define SPX_OFFSET_KP_ADDR1 13
+
+// The byte used to specify the chain address (which Winternitz chain).
+#define SPX_OFFSET_CHAIN_ADDR 17
+
+// The byte used to specify the hash address (where in the Winternitz chain).
+#define SPX_OFFSET_HASH_ADDR 21
+
+// The byte used to specify the height of this node in the FORS or Merkle tree.
+#define SPX_OFFSET_TREE_HGT 17
+
+// The start of the 4 byte field used to specify the node in the FORS or Merkle
+// tree.
+#define SPX_OFFSET_TREE_INDEX 18
+
+
+void spx_set_chain_addr(uint8_t addr[32], uint32_t chain) {
+  addr[SPX_OFFSET_CHAIN_ADDR] = (uint8_t)chain;
+}
+
+void spx_set_hash_addr(uint8_t addr[32], uint32_t hash) {
+  addr[SPX_OFFSET_HASH_ADDR] = (uint8_t)hash;
+}
+
+void spx_set_keypair_addr(uint8_t addr[32], uint32_t keypair) {
+  addr[SPX_OFFSET_KP_ADDR2] = (uint8_t)(keypair >> 8);
+  addr[SPX_OFFSET_KP_ADDR1] = (uint8_t)keypair;
+}
+
+void spx_copy_keypair_addr(uint8_t out[32], const uint8_t in[32]) {
+  memcpy(out, in, SPX_OFFSET_TREE + 8);
+  out[SPX_OFFSET_KP_ADDR2] = in[SPX_OFFSET_KP_ADDR2];
+  out[SPX_OFFSET_KP_ADDR1] = in[SPX_OFFSET_KP_ADDR1];
+}
+
+void spx_set_layer_addr(uint8_t addr[32], uint32_t layer) {
+  addr[SPX_OFFSET_LAYER] = (uint8_t)layer;
+}
+
+void spx_set_tree_addr(uint8_t addr[32], uint64_t tree) {
+  spx_uint64_to_len_bytes(&addr[SPX_OFFSET_TREE], 8, tree);
+}
+
+void spx_set_type(uint8_t addr[32], uint32_t type) {
+  // NIST draft relies on this setting parts of the address to 0, so we do it
+  // here to avoid confusion.
+  //
+  // The behavior here is only correct for the SHA2 instantiations.
+  memset(addr + 10, 0, 12);
+  addr[SPX_OFFSET_TYPE] = (uint8_t)type;
+}
+
+void spx_set_tree_height(uint8_t addr[32], uint32_t tree_height) {
+  addr[SPX_OFFSET_TREE_HGT] = (uint8_t)tree_height;
+}
+
+void spx_set_tree_index(uint8_t addr[32], uint32_t tree_index) {
+  CRYPTO_store_u32_be(&addr[SPX_OFFSET_TREE_INDEX], tree_index);
+}
+
+uint32_t spx_get_tree_index(uint8_t addr[32]) {
+  return CRYPTO_load_u32_be(addr + SPX_OFFSET_TREE_INDEX);
+}