Clean up key generation
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Joost Rijneveld
parent
270e6cd753
commit
a9fe0e43fe
136
xmss_core.c
136
xmss_core.c
@ -11,50 +11,56 @@
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#include "xmss_core.h"
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/**
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* Merkle's TreeHash algorithm. The address only needs to initialize the first
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* 78 bits of addr. Everything else will be set by treehash.
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* Currently only used for key generation.
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* Merkle's TreeHash algorithm. Currently only used for key generation.
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* Computes the root node of the top-most subtree.
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*/
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static void treehash(const xmss_params *params, unsigned char *node, uint32_t index, const unsigned char *sk_seed, const unsigned char *pub_seed, const uint32_t addr[8])
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static void treehash_root(const xmss_params *params, unsigned char *root,
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const unsigned char *sk_seed,
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const unsigned char *pub_seed)
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{
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uint32_t idx = index;
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// Use three different addresses because at this point we use all three formats in parallel
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uint32_t ots_addr[8];
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uint32_t ltree_addr[8];
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uint32_t node_addr[8];
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// only copy layer and tree address parts
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memcpy(ots_addr, addr, 12);
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// type = ots
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unsigned char stack[(params->tree_height+1)*params->n];
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unsigned int heights[params->tree_height+1];
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unsigned int offset = 0;
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/* The subtree has at most 2^20 leafs, so uint32_t suffices. */
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uint32_t idx;
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/* We need all three types of addresses in parallel. */
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uint32_t ots_addr[8] = {0};
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uint32_t ltree_addr[8] = {0};
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uint32_t node_addr[8] = {0};
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/* To support the multi-tree setting, select the top tree. */
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set_layer_addr(ots_addr, params->d - 1);
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set_layer_addr(ltree_addr, params->d - 1);
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set_layer_addr(node_addr, params->d - 1);
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set_type(ots_addr, 0);
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memcpy(ltree_addr, addr, 12);
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set_type(ltree_addr, 1);
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memcpy(node_addr, addr, 12);
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set_type(node_addr, 2);
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uint32_t lastnode, i;
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unsigned char stack[(params->tree_height+1)*params->n];
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uint16_t stacklevels[params->tree_height+1];
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unsigned int stackoffset=0;
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lastnode = idx+(1 << params->tree_height);
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for (; idx < lastnode; idx++) {
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for (idx = 0; idx < (uint32_t)(1 << params->tree_height); idx++) {
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/* Add the next leaf node to the stack. */
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set_ltree_addr(ltree_addr, idx);
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set_ots_addr(ots_addr, idx);
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gen_leaf_wots(params, stack+stackoffset*params->n, sk_seed, pub_seed, ltree_addr, ots_addr);
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stacklevels[stackoffset] = 0;
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stackoffset++;
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while (stackoffset>1 && stacklevels[stackoffset-1] == stacklevels[stackoffset-2]) {
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set_tree_height(node_addr, stacklevels[stackoffset-1]);
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set_tree_index(node_addr, (idx >> (stacklevels[stackoffset-1]+1)));
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hash_h(params, stack+(stackoffset-2)*params->n, stack+(stackoffset-2)*params->n, pub_seed, node_addr);
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stacklevels[stackoffset-2]++;
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stackoffset--;
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gen_leaf_wots(params, stack + offset*params->n,
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sk_seed, pub_seed, ltree_addr, ots_addr);
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heights[offset] = 0;
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offset++;
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/* While the top-most nodes are of equal height.. */
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while (offset >= 2 && heights[offset - 1] == heights[offset - 2]) {
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/* Hash the top-most nodes from the stack together. */
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set_tree_height(node_addr, heights[offset - 1]);
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set_tree_index(node_addr, (idx >> (heights[offset - 1] + 1)));
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hash_h(params, stack + (offset-2)*params->n,
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stack + (offset-2)*params->n, pub_seed, node_addr);
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/* Note that the top-most node is now one layer higher. */
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heights[offset-2]++;
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offset--;
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}
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}
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for (i = 0; i < params->n; i++) {
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node[i] = stack[i];
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}
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memcpy(root, stack, params->n);
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}
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/**
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@ -112,29 +118,26 @@ static void compute_authpath_wots(const xmss_params *params, unsigned char *root
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memcpy(root, tree+params->n, params->n);
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}
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/*
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* Generates a XMSS key pair for a given parameter set.
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* Format sk: [(32bit) idx || SK_SEED || SK_PRF || PUB_SEED || root]
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* Format pk: [root || PUB_SEED] omitting algo oid.
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* Format sk: [(32bit) index || SK_SEED || SK_PRF || PUB_SEED || root]
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* Format pk: [root || PUB_SEED], omitting algorithm OID.
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*/
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int xmss_core_keypair(const xmss_params *params, unsigned char *pk, unsigned char *sk)
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int xmss_core_keypair(const xmss_params *params,
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unsigned char *pk, unsigned char *sk)
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{
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// Set idx = 0
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sk[0] = 0;
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sk[1] = 0;
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sk[2] = 0;
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sk[3] = 0;
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// Init SK_SEED (params->n byte), SK_PRF (params->n byte), and PUB_SEED (params->n byte)
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randombytes(sk+4, 3*params->n);
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// Copy PUB_SEED to public key
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memcpy(pk+params->n, sk+4+2*params->n, params->n);
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/* Initialize index to 0. */
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memset(sk, 0, params->index_len);
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sk += 4;
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/* Initialize SK_SEED, SK_PRF and PUB_SEED. */
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randombytes(sk, 3 * params->n);
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memcpy(pk + params->n, sk + 2*params->n, params->n);
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/* Compute root node. */
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treehash_root(params, pk, sk, pk + params->n);
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memcpy(sk + 3*params->n, pk, params->n);
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uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
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// Compute root
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treehash(params, pk, 0, sk+4, sk+4+2*params->n, addr);
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// copy root to sk
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memcpy(sk+4+3*params->n, pk, params->n);
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return 0;
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}
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@ -242,28 +245,23 @@ int xmss_core_sign(const xmss_params *params, unsigned char *sk, unsigned char *
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/*
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* Generates a XMSSMT key pair for a given parameter set.
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* Format sk: [(ceil(h/8) bit) idx || SK_SEED || SK_PRF || PUB_SEED]
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* Format pk: [root || PUB_SEED] omitting algo oid.
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* Format sk: [(ceil(h/8) bit) index || SK_SEED || SK_PRF || PUB_SEED]
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* Format pk: [root || PUB_SEED] omitting algorithm OID.
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*/
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int xmssmt_core_keypair(const xmss_params *params, unsigned char *pk, unsigned char *sk)
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{
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uint16_t i;
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// Set idx = 0
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for (i = 0; i < params->index_len; i++) {
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sk[i] = 0;
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}
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// Init SK_SEED (params->n byte), SK_PRF (params->n byte), and PUB_SEED (params->n byte)
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randombytes(sk+params->index_len, 3*params->n);
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// Copy PUB_SEED to public key
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memcpy(pk+params->n, sk+params->index_len+2*params->n, params->n);
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/* Initialize index to 0. */
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memset(sk, 0, params->index_len);
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sk += 4;
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// Set address to point on the single tree on layer d-1
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uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
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set_layer_addr(addr, (params->d-1));
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/* Initialize SK_SEED, SK_PRF and PUB_SEED. */
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randombytes(sk, 3 * params->n);
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memcpy(pk + params->n, sk + 2*params->n, params->n);
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/* Compute root node of the top-most subtree. */
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treehash_root(params, pk, sk, pk + params->n);
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memcpy(sk + 3*params->n, pk, params->n);
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// Compute root
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treehash(params, pk, 0, sk+params->index_len, pk+params->n, addr);
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memcpy(sk+params->index_len+3*params->n, pk, params->n);
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return 0;
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}
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