blob: 421b39a37a9e4a8071989d3dafe90a95eab71982 [file] [log] [blame]
/* $OpenBSD: xmss_fast.c,v 1.3 2018/03/22 07:06:11 markus Exp $ */
/*
xmss_fast.c version 20160722
Andreas Hülsing
Joost Rijneveld
Public domain.
*/
#include "includes.h"
#ifdef WITH_XMSS
#include <stdlib.h>
#include <string.h>
#ifdef HAVE_STDINT_H
# include <stdint.h>
#endif
#include "xmss_fast.h"
#include "crypto_api.h"
#include "xmss_wots.h"
#include "xmss_hash.h"
#include "xmss_commons.h"
#include "xmss_hash_address.h"
// For testing
#include "stdio.h"
/**
* Used for pseudorandom keygeneration,
* generates the seed for the WOTS keypair at address addr
*
* takes n byte sk_seed and returns n byte seed using 32 byte address addr.
*/
static void get_seed(unsigned char *seed, const unsigned char *sk_seed, int n, uint32_t addr[8])
{
unsigned char bytes[32];
// Make sure that chain addr, hash addr, and key bit are 0!
setChainADRS(addr,0);
setHashADRS(addr,0);
setKeyAndMask(addr,0);
// Generate pseudorandom value
addr_to_byte(bytes, addr);
prf(seed, bytes, sk_seed, n);
}
/**
* Initialize xmss params struct
* parameter names are the same as in the draft
* parameter k is K as used in the BDS algorithm
*/
int xmss_set_params(xmss_params *params, int n, int h, int w, int k)
{
if (k >= h || k < 2 || (h - k) % 2) {
fprintf(stderr, "For BDS traversal, H - K must be even, with H > K >= 2!\n");
return 1;
}
params->h = h;
params->n = n;
params->k = k;
wots_params wots_par;
wots_set_params(&wots_par, n, w);
params->wots_par = wots_par;
return 0;
}
/**
* Initialize BDS state struct
* parameter names are the same as used in the description of the BDS traversal
*/
void xmss_set_bds_state(bds_state *state, unsigned char *stack, int stackoffset, unsigned char *stacklevels, unsigned char *auth, unsigned char *keep, treehash_inst *treehash, unsigned char *retain, int next_leaf)
{
state->stack = stack;
state->stackoffset = stackoffset;
state->stacklevels = stacklevels;
state->auth = auth;
state->keep = keep;
state->treehash = treehash;
state->retain = retain;
state->next_leaf = next_leaf;
}
/**
* Initialize xmssmt_params struct
* parameter names are the same as in the draft
*
* Especially h is the total tree height, i.e. the XMSS trees have height h/d
*/
int xmssmt_set_params(xmssmt_params *params, int n, int h, int d, int w, int k)
{
if (h % d) {
fprintf(stderr, "d must divide h without remainder!\n");
return 1;
}
params->h = h;
params->d = d;
params->n = n;
params->index_len = (h + 7) / 8;
xmss_params xmss_par;
if (xmss_set_params(&xmss_par, n, (h/d), w, k)) {
return 1;
}
params->xmss_par = xmss_par;
return 0;
}
/**
* Computes a leaf from a WOTS public key using an L-tree.
*/
static void l_tree(unsigned char *leaf, unsigned char *wots_pk, const xmss_params *params, const unsigned char *pub_seed, uint32_t addr[8])
{
unsigned int l = params->wots_par.len;
unsigned int n = params->n;
uint32_t i = 0;
uint32_t height = 0;
uint32_t bound;
//ADRS.setTreeHeight(0);
setTreeHeight(addr, height);
while (l > 1) {
bound = l >> 1; //floor(l / 2);
for (i = 0; i < bound; i++) {
//ADRS.setTreeIndex(i);
setTreeIndex(addr, i);
//wots_pk[i] = RAND_HASH(pk[2i], pk[2i + 1], SEED, ADRS);
hash_h(wots_pk+i*n, wots_pk+i*2*n, pub_seed, addr, n);
}
//if ( l % 2 == 1 ) {
if (l & 1) {
//pk[floor(l / 2) + 1] = pk[l];
memcpy(wots_pk+(l>>1)*n, wots_pk+(l-1)*n, n);
//l = ceil(l / 2);
l=(l>>1)+1;
}
else {
//l = ceil(l / 2);
l=(l>>1);
}
//ADRS.setTreeHeight(ADRS.getTreeHeight() + 1);
height++;
setTreeHeight(addr, height);
}
//return pk[0];
memcpy(leaf, wots_pk, n);
}
/**
* Computes the leaf at a given address. First generates the WOTS key pair, then computes leaf using l_tree. As this happens position independent, we only require that addr encodes the right ltree-address.
*/
static void gen_leaf_wots(unsigned char *leaf, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, uint32_t ltree_addr[8], uint32_t ots_addr[8])
{
unsigned char seed[params->n];
unsigned char pk[params->wots_par.keysize];
get_seed(seed, sk_seed, params->n, ots_addr);
wots_pkgen(pk, seed, &(params->wots_par), pub_seed, ots_addr);
l_tree(leaf, pk, params, pub_seed, ltree_addr);
}
static int treehash_minheight_on_stack(bds_state* state, const xmss_params *params, const treehash_inst *treehash) {
unsigned int r = params->h, i;
for (i = 0; i < treehash->stackusage; i++) {
if (state->stacklevels[state->stackoffset - i - 1] < r) {
r = state->stacklevels[state->stackoffset - i - 1];
}
}
return r;
}
/**
* Merkle's TreeHash algorithm. The address only needs to initialize the first 78 bits of addr. Everything else will be set by treehash.
* Currently only used for key generation.
*
*/
static void treehash_setup(unsigned char *node, int height, int index, bds_state *state, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, const uint32_t addr[8])
{
unsigned int idx = index;
unsigned int n = params->n;
unsigned int h = params->h;
unsigned int k = params->k;
// use three different addresses because at this point we use all three formats in parallel
uint32_t ots_addr[8];
uint32_t ltree_addr[8];
uint32_t node_addr[8];
// only copy layer and tree address parts
memcpy(ots_addr, addr, 12);
// type = ots
setType(ots_addr, 0);
memcpy(ltree_addr, addr, 12);
setType(ltree_addr, 1);
memcpy(node_addr, addr, 12);
setType(node_addr, 2);
uint32_t lastnode, i;
unsigned char stack[(height+1)*n];
unsigned int stacklevels[height+1];
unsigned int stackoffset=0;
unsigned int nodeh;
lastnode = idx+(1<<height);
for (i = 0; i < h-k; i++) {
state->treehash[i].h = i;
state->treehash[i].completed = 1;
state->treehash[i].stackusage = 0;
}
i = 0;
for (; idx < lastnode; idx++) {
setLtreeADRS(ltree_addr, idx);
setOTSADRS(ots_addr, idx);
gen_leaf_wots(stack+stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr);
stacklevels[stackoffset] = 0;
stackoffset++;
if (h - k > 0 && i == 3) {
memcpy(state->treehash[0].node, stack+stackoffset*n, n);
}
while (stackoffset>1 && stacklevels[stackoffset-1] == stacklevels[stackoffset-2])
{
nodeh = stacklevels[stackoffset-1];
if (i >> nodeh == 1) {
memcpy(state->auth + nodeh*n, stack+(stackoffset-1)*n, n);
}
else {
if (nodeh < h - k && i >> nodeh == 3) {
memcpy(state->treehash[nodeh].node, stack+(stackoffset-1)*n, n);
}
else if (nodeh >= h - k) {
memcpy(state->retain + ((1 << (h - 1 - nodeh)) + nodeh - h + (((i >> nodeh) - 3) >> 1)) * n, stack+(stackoffset-1)*n, n);
}
}
setTreeHeight(node_addr, stacklevels[stackoffset-1]);
setTreeIndex(node_addr, (idx >> (stacklevels[stackoffset-1]+1)));
hash_h(stack+(stackoffset-2)*n, stack+(stackoffset-2)*n, pub_seed,
node_addr, n);
stacklevels[stackoffset-2]++;
stackoffset--;
}
i++;
}
for (i = 0; i < n; i++)
node[i] = stack[i];
}
static void treehash_update(treehash_inst *treehash, bds_state *state, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, const uint32_t addr[8]) {
int n = params->n;
uint32_t ots_addr[8];
uint32_t ltree_addr[8];
uint32_t node_addr[8];
// only copy layer and tree address parts
memcpy(ots_addr, addr, 12);
// type = ots
setType(ots_addr, 0);
memcpy(ltree_addr, addr, 12);
setType(ltree_addr, 1);
memcpy(node_addr, addr, 12);
setType(node_addr, 2);
setLtreeADRS(ltree_addr, treehash->next_idx);
setOTSADRS(ots_addr, treehash->next_idx);
unsigned char nodebuffer[2 * n];
unsigned int nodeheight = 0;
gen_leaf_wots(nodebuffer, sk_seed, params, pub_seed, ltree_addr, ots_addr);
while (treehash->stackusage > 0 && state->stacklevels[state->stackoffset-1] == nodeheight) {
memcpy(nodebuffer + n, nodebuffer, n);
memcpy(nodebuffer, state->stack + (state->stackoffset-1)*n, n);
setTreeHeight(node_addr, nodeheight);
setTreeIndex(node_addr, (treehash->next_idx >> (nodeheight+1)));
hash_h(nodebuffer, nodebuffer, pub_seed, node_addr, n);
nodeheight++;
treehash->stackusage--;
state->stackoffset--;
}
if (nodeheight == treehash->h) { // this also implies stackusage == 0
memcpy(treehash->node, nodebuffer, n);
treehash->completed = 1;
}
else {
memcpy(state->stack + state->stackoffset*n, nodebuffer, n);
treehash->stackusage++;
state->stacklevels[state->stackoffset] = nodeheight;
state->stackoffset++;
treehash->next_idx++;
}
}
/**
* Computes a root node given a leaf and an authapth
*/
static void validate_authpath(unsigned char *root, const unsigned char *leaf, unsigned long leafidx, const unsigned char *authpath, const xmss_params *params, const unsigned char *pub_seed, uint32_t addr[8])
{
unsigned int n = params->n;
uint32_t i, j;
unsigned char buffer[2*n];
// If leafidx is odd (last bit = 1), current path element is a right child and authpath has to go to the left.
// Otherwise, it is the other way around
if (leafidx & 1) {
for (j = 0; j < n; j++)
buffer[n+j] = leaf[j];
for (j = 0; j < n; j++)
buffer[j] = authpath[j];
}
else {
for (j = 0; j < n; j++)
buffer[j] = leaf[j];
for (j = 0; j < n; j++)
buffer[n+j] = authpath[j];
}
authpath += n;
for (i=0; i < params->h-1; i++) {
setTreeHeight(addr, i);
leafidx >>= 1;
setTreeIndex(addr, leafidx);
if (leafidx&1) {
hash_h(buffer+n, buffer, pub_seed, addr, n);
for (j = 0; j < n; j++)
buffer[j] = authpath[j];
}
else {
hash_h(buffer, buffer, pub_seed, addr, n);
for (j = 0; j < n; j++)
buffer[j+n] = authpath[j];
}
authpath += n;
}
setTreeHeight(addr, (params->h-1));
leafidx >>= 1;
setTreeIndex(addr, leafidx);
hash_h(root, buffer, pub_seed, addr, n);
}
/**
* Performs one treehash update on the instance that needs it the most.
* Returns 1 if such an instance was not found
**/
static char bds_treehash_update(bds_state *state, unsigned int updates, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, const uint32_t addr[8]) {
uint32_t i, j;
unsigned int level, l_min, low;
unsigned int h = params->h;
unsigned int k = params->k;
unsigned int used = 0;
for (j = 0; j < updates; j++) {
l_min = h;
level = h - k;
for (i = 0; i < h - k; i++) {
if (state->treehash[i].completed) {
low = h;
}
else if (state->treehash[i].stackusage == 0) {
low = i;
}
else {
low = treehash_minheight_on_stack(state, params, &(state->treehash[i]));
}
if (low < l_min) {
level = i;
l_min = low;
}
}
if (level == h - k) {
break;
}
treehash_update(&(state->treehash[level]), state, sk_seed, params, pub_seed, addr);
used++;
}
return updates - used;
}
/**
* Updates the state (typically NEXT_i) by adding a leaf and updating the stack
* Returns 1 if all leaf nodes have already been processed
**/
static char bds_state_update(bds_state *state, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, const uint32_t addr[8]) {
uint32_t ltree_addr[8];
uint32_t node_addr[8];
uint32_t ots_addr[8];
int n = params->n;
int h = params->h;
int k = params->k;
int nodeh;
int idx = state->next_leaf;
if (idx == 1 << h) {
return 1;
}
// only copy layer and tree address parts
memcpy(ots_addr, addr, 12);
// type = ots
setType(ots_addr, 0);
memcpy(ltree_addr, addr, 12);
setType(ltree_addr, 1);
memcpy(node_addr, addr, 12);
setType(node_addr, 2);
setOTSADRS(ots_addr, idx);
setLtreeADRS(ltree_addr, idx);
gen_leaf_wots(state->stack+state->stackoffset*n, sk_seed, params, pub_seed, ltree_addr, ots_addr);
state->stacklevels[state->stackoffset] = 0;
state->stackoffset++;
if (h - k > 0 && idx == 3) {
memcpy(state->treehash[0].node, state->stack+state->stackoffset*n, n);
}
while (state->stackoffset>1 && state->stacklevels[state->stackoffset-1] == state->stacklevels[state->stackoffset-2]) {
nodeh = state->stacklevels[state->stackoffset-1];
if (idx >> nodeh == 1) {
memcpy(state->auth + nodeh*n, state->stack+(state->stackoffset-1)*n, n);
}
else {
if (nodeh < h - k && idx >> nodeh == 3) {
memcpy(state->treehash[nodeh].node, state->stack+(state->stackoffset-1)*n, n);
}
else if (nodeh >= h - k) {
memcpy(state->retain + ((1 << (h - 1 - nodeh)) + nodeh - h + (((idx >> nodeh) - 3) >> 1)) * n, state->stack+(state->stackoffset-1)*n, n);
}
}
setTreeHeight(node_addr, state->stacklevels[state->stackoffset-1]);
setTreeIndex(node_addr, (idx >> (state->stacklevels[state->stackoffset-1]+1)));
hash_h(state->stack+(state->stackoffset-2)*n, state->stack+(state->stackoffset-2)*n, pub_seed, node_addr, n);
state->stacklevels[state->stackoffset-2]++;
state->stackoffset--;
}
state->next_leaf++;
return 0;
}
/**
* Returns the auth path for node leaf_idx and computes the auth path for the
* next leaf node, using the algorithm described by Buchmann, Dahmen and Szydlo
* in "Post Quantum Cryptography", Springer 2009.
*/
static void bds_round(bds_state *state, const unsigned long leaf_idx, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, uint32_t addr[8])
{
unsigned int i;
unsigned int n = params->n;
unsigned int h = params->h;
unsigned int k = params->k;
unsigned int tau = h;
unsigned int startidx;
unsigned int offset, rowidx;
unsigned char buf[2 * n];
uint32_t ots_addr[8];
uint32_t ltree_addr[8];
uint32_t node_addr[8];
// only copy layer and tree address parts
memcpy(ots_addr, addr, 12);
// type = ots
setType(ots_addr, 0);
memcpy(ltree_addr, addr, 12);
setType(ltree_addr, 1);
memcpy(node_addr, addr, 12);
setType(node_addr, 2);
for (i = 0; i < h; i++) {
if (! ((leaf_idx >> i) & 1)) {
tau = i;
break;
}
}
if (tau > 0) {
memcpy(buf, state->auth + (tau-1) * n, n);
// we need to do this before refreshing state->keep to prevent overwriting
memcpy(buf + n, state->keep + ((tau-1) >> 1) * n, n);
}
if (!((leaf_idx >> (tau + 1)) & 1) && (tau < h - 1)) {
memcpy(state->keep + (tau >> 1)*n, state->auth + tau*n, n);
}
if (tau == 0) {
setLtreeADRS(ltree_addr, leaf_idx);
setOTSADRS(ots_addr, leaf_idx);
gen_leaf_wots(state->auth, sk_seed, params, pub_seed, ltree_addr, ots_addr);
}
else {
setTreeHeight(node_addr, (tau-1));
setTreeIndex(node_addr, leaf_idx >> tau);
hash_h(state->auth + tau * n, buf, pub_seed, node_addr, n);
for (i = 0; i < tau; i++) {
if (i < h - k) {
memcpy(state->auth + i * n, state->treehash[i].node, n);
}
else {
offset = (1 << (h - 1 - i)) + i - h;
rowidx = ((leaf_idx >> i) - 1) >> 1;
memcpy(state->auth + i * n, state->retain + (offset + rowidx) * n, n);
}
}
for (i = 0; i < ((tau < h - k) ? tau : (h - k)); i++) {
startidx = leaf_idx + 1 + 3 * (1 << i);
if (startidx < 1U << h) {
state->treehash[i].h = i;
state->treehash[i].next_idx = startidx;
state->treehash[i].completed = 0;
state->treehash[i].stackusage = 0;
}
}
}
}
/*
* Generates a XMSS key pair for a given parameter set.
* Format sk: [(32bit) idx || SK_SEED || SK_PRF || PUB_SEED || root]
* Format pk: [root || PUB_SEED] omitting algo oid.
*/
int xmss_keypair(unsigned char *pk, unsigned char *sk, bds_state *state, xmss_params *params)
{
unsigned int n = params->n;
// Set idx = 0
sk[0] = 0;
sk[1] = 0;
sk[2] = 0;
sk[3] = 0;
// Init SK_SEED (n byte), SK_PRF (n byte), and PUB_SEED (n byte)
randombytes(sk+4, 3*n);
// Copy PUB_SEED to public key
memcpy(pk+n, sk+4+2*n, n);
uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
// Compute root
treehash_setup(pk, params->h, 0, state, sk+4, params, sk+4+2*n, addr);
// copy root to sk
memcpy(sk+4+3*n, pk, n);
return 0;
}
/**
* Signs a message.
* Returns
* 1. an array containing the signature followed by the message AND
* 2. an updated secret key!
*
*/
int xmss_sign(unsigned char *sk, bds_state *state, unsigned char *sig_msg, unsigned long long *sig_msg_len, const unsigned char *msg, unsigned long long msglen, const xmss_params *params)
{
unsigned int h = params->h;
unsigned int n = params->n;
unsigned int k = params->k;
uint16_t i = 0;
// Extract SK
unsigned long idx = ((unsigned long)sk[0] << 24) | ((unsigned long)sk[1] << 16) | ((unsigned long)sk[2] << 8) | sk[3];
unsigned char sk_seed[n];
memcpy(sk_seed, sk+4, n);
unsigned char sk_prf[n];
memcpy(sk_prf, sk+4+n, n);
unsigned char pub_seed[n];
memcpy(pub_seed, sk+4+2*n, n);
// index as 32 bytes string
unsigned char idx_bytes_32[32];
to_byte(idx_bytes_32, idx, 32);
unsigned char hash_key[3*n];
// Update SK
sk[0] = ((idx + 1) >> 24) & 255;
sk[1] = ((idx + 1) >> 16) & 255;
sk[2] = ((idx + 1) >> 8) & 255;
sk[3] = (idx + 1) & 255;
// -- Secret key for this non-forward-secure version is now updated.
// -- A productive implementation should use a file handle instead and write the updated secret key at this point!
// Init working params
unsigned char R[n];
unsigned char msg_h[n];
unsigned char ots_seed[n];
uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
// ---------------------------------
// Message Hashing
// ---------------------------------
// Message Hash:
// First compute pseudorandom value
prf(R, idx_bytes_32, sk_prf, n);
// Generate hash key (R || root || idx)
memcpy(hash_key, R, n);
memcpy(hash_key+n, sk+4+3*n, n);
to_byte(hash_key+2*n, idx, n);
// Then use it for message digest
h_msg(msg_h, msg, msglen, hash_key, 3*n, n);
// Start collecting signature
*sig_msg_len = 0;
// Copy index to signature
sig_msg[0] = (idx >> 24) & 255;
sig_msg[1] = (idx >> 16) & 255;
sig_msg[2] = (idx >> 8) & 255;
sig_msg[3] = idx & 255;
sig_msg += 4;
*sig_msg_len += 4;
// Copy R to signature
for (i = 0; i < n; i++)
sig_msg[i] = R[i];
sig_msg += n;
*sig_msg_len += n;
// ----------------------------------
// Now we start to "really sign"
// ----------------------------------
// Prepare Address
setType(ots_addr, 0);
setOTSADRS(ots_addr, idx);
// Compute seed for OTS key pair
get_seed(ots_seed, sk_seed, n, ots_addr);
// Compute WOTS signature
wots_sign(sig_msg, msg_h, ots_seed, &(params->wots_par), pub_seed, ots_addr);
sig_msg += params->wots_par.keysize;
*sig_msg_len += params->wots_par.keysize;
// the auth path was already computed during the previous round
memcpy(sig_msg, state->auth, h*n);
if (idx < (1U << h) - 1) {
bds_round(state, idx, sk_seed, params, pub_seed, ots_addr);
bds_treehash_update(state, (h - k) >> 1, sk_seed, params, pub_seed, ots_addr);
}
/* TODO: save key/bds state here! */
sig_msg += params->h*n;
*sig_msg_len += params->h*n;
//Whipe secret elements?
//zerobytes(tsk, CRYPTO_SECRETKEYBYTES);
memcpy(sig_msg, msg, msglen);
*sig_msg_len += msglen;
return 0;
}
/**
* Verifies a given message signature pair under a given public key.
*/
int xmss_sign_open(unsigned char *msg, unsigned long long *msglen, const unsigned char *sig_msg, unsigned long long sig_msg_len, const unsigned char *pk, const xmss_params *params)
{
unsigned int n = params->n;
unsigned long long i, m_len;
unsigned long idx=0;
unsigned char wots_pk[params->wots_par.keysize];
unsigned char pkhash[n];
unsigned char root[n];
unsigned char msg_h[n];
unsigned char hash_key[3*n];
unsigned char pub_seed[n];
memcpy(pub_seed, pk+n, n);
// Init addresses
uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
uint32_t ltree_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
uint32_t node_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
setType(ots_addr, 0);
setType(ltree_addr, 1);
setType(node_addr, 2);
// Extract index
idx = ((unsigned long)sig_msg[0] << 24) | ((unsigned long)sig_msg[1] << 16) | ((unsigned long)sig_msg[2] << 8) | sig_msg[3];
printf("verify:: idx = %lu\n", idx);
// Generate hash key (R || root || idx)
memcpy(hash_key, sig_msg+4,n);
memcpy(hash_key+n, pk, n);
to_byte(hash_key+2*n, idx, n);
sig_msg += (n+4);
sig_msg_len -= (n+4);
// hash message
unsigned long long tmp_sig_len = params->wots_par.keysize+params->h*n;
m_len = sig_msg_len - tmp_sig_len;
h_msg(msg_h, sig_msg + tmp_sig_len, m_len, hash_key, 3*n, n);
//-----------------------
// Verify signature
//-----------------------
// Prepare Address
setOTSADRS(ots_addr, idx);
// Check WOTS signature
wots_pkFromSig(wots_pk, sig_msg, msg_h, &(params->wots_par), pub_seed, ots_addr);
sig_msg += params->wots_par.keysize;
sig_msg_len -= params->wots_par.keysize;
// Compute Ltree
setLtreeADRS(ltree_addr, idx);
l_tree(pkhash, wots_pk, params, pub_seed, ltree_addr);
// Compute root
validate_authpath(root, pkhash, idx, sig_msg, params, pub_seed, node_addr);
sig_msg += params->h*n;
sig_msg_len -= params->h*n;
for (i = 0; i < n; i++)
if (root[i] != pk[i])
goto fail;
*msglen = sig_msg_len;
for (i = 0; i < *msglen; i++)
msg[i] = sig_msg[i];
return 0;
fail:
*msglen = sig_msg_len;
for (i = 0; i < *msglen; i++)
msg[i] = 0;
*msglen = -1;
return -1;
}
/*
* Generates a XMSSMT key pair for a given parameter set.
* Format sk: [(ceil(h/8) bit) idx || SK_SEED || SK_PRF || PUB_SEED || root]
* Format pk: [root || PUB_SEED] omitting algo oid.
*/
int xmssmt_keypair(unsigned char *pk, unsigned char *sk, bds_state *states, unsigned char *wots_sigs, xmssmt_params *params)
{
unsigned int n = params->n;
unsigned int i;
unsigned char ots_seed[params->n];
// Set idx = 0
for (i = 0; i < params->index_len; i++) {
sk[i] = 0;
}
// Init SK_SEED (n byte), SK_PRF (n byte), and PUB_SEED (n byte)
randombytes(sk+params->index_len, 3*n);
// Copy PUB_SEED to public key
memcpy(pk+n, sk+params->index_len+2*n, n);
// Set address to point on the single tree on layer d-1
uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
setLayerADRS(addr, (params->d-1));
// Set up state and compute wots signatures for all but topmost tree root
for (i = 0; i < params->d - 1; i++) {
// Compute seed for OTS key pair
treehash_setup(pk, params->xmss_par.h, 0, states + i, sk+params->index_len, &(params->xmss_par), pk+n, addr);
setLayerADRS(addr, (i+1));
get_seed(ots_seed, sk+params->index_len, n, addr);
wots_sign(wots_sigs + i*params->xmss_par.wots_par.keysize, pk, ots_seed, &(params->xmss_par.wots_par), pk+n, addr);
}
treehash_setup(pk, params->xmss_par.h, 0, states + i, sk+params->index_len, &(params->xmss_par), pk+n, addr);
memcpy(sk+params->index_len+3*n, pk, n);
return 0;
}
/**
* Signs a message.
* Returns
* 1. an array containing the signature followed by the message AND
* 2. an updated secret key!
*
*/
int xmssmt_sign(unsigned char *sk, bds_state *states, unsigned char *wots_sigs, unsigned char *sig_msg, unsigned long long *sig_msg_len, const unsigned char *msg, unsigned long long msglen, const xmssmt_params *params)
{
unsigned int n = params->n;
unsigned int tree_h = params->xmss_par.h;
unsigned int h = params->h;
unsigned int k = params->xmss_par.k;
unsigned int idx_len = params->index_len;
uint64_t idx_tree;
uint32_t idx_leaf;
uint64_t i, j;
int needswap_upto = -1;
unsigned int updates;
unsigned char sk_seed[n];
unsigned char sk_prf[n];
unsigned char pub_seed[n];
// Init working params
unsigned char R[n];
unsigned char msg_h[n];
unsigned char hash_key[3*n];
unsigned char ots_seed[n];
uint32_t addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
unsigned char idx_bytes_32[32];
bds_state tmp;
// Extract SK
unsigned long long idx = 0;
for (i = 0; i < idx_len; i++) {
idx |= ((unsigned long long)sk[i]) << 8*(idx_len - 1 - i);
}
memcpy(sk_seed, sk+idx_len, n);
memcpy(sk_prf, sk+idx_len+n, n);
memcpy(pub_seed, sk+idx_len+2*n, n);
// Update SK
for (i = 0; i < idx_len; i++) {
sk[i] = ((idx + 1) >> 8*(idx_len - 1 - i)) & 255;
}
// -- Secret key for this non-forward-secure version is now updated.
// -- A productive implementation should use a file handle instead and write the updated secret key at this point!
// ---------------------------------
// Message Hashing
// ---------------------------------
// Message Hash:
// First compute pseudorandom value
to_byte(idx_bytes_32, idx, 32);
prf(R, idx_bytes_32, sk_prf, n);
// Generate hash key (R || root || idx)
memcpy(hash_key, R, n);
memcpy(hash_key+n, sk+idx_len+3*n, n);
to_byte(hash_key+2*n, idx, n);
// Then use it for message digest
h_msg(msg_h, msg, msglen, hash_key, 3*n, n);
// Start collecting signature
*sig_msg_len = 0;
// Copy index to signature
for (i = 0; i < idx_len; i++) {
sig_msg[i] = (idx >> 8*(idx_len - 1 - i)) & 255;
}
sig_msg += idx_len;
*sig_msg_len += idx_len;
// Copy R to signature
for (i = 0; i < n; i++)
sig_msg[i] = R[i];
sig_msg += n;
*sig_msg_len += n;
// ----------------------------------
// Now we start to "really sign"
// ----------------------------------
// Handle lowest layer separately as it is slightly different...
// Prepare Address
setType(ots_addr, 0);
idx_tree = idx >> tree_h;
idx_leaf = (idx & ((1 << tree_h)-1));
setLayerADRS(ots_addr, 0);
setTreeADRS(ots_addr, idx_tree);
setOTSADRS(ots_addr, idx_leaf);
// Compute seed for OTS key pair
get_seed(ots_seed, sk_seed, n, ots_addr);
// Compute WOTS signature
wots_sign(sig_msg, msg_h, ots_seed, &(params->xmss_par.wots_par), pub_seed, ots_addr);
sig_msg += params->xmss_par.wots_par.keysize;
*sig_msg_len += params->xmss_par.wots_par.keysize;
memcpy(sig_msg, states[0].auth, tree_h*n);
sig_msg += tree_h*n;
*sig_msg_len += tree_h*n;
// prepare signature of remaining layers
for (i = 1; i < params->d; i++) {
// put WOTS signature in place
memcpy(sig_msg, wots_sigs + (i-1)*params->xmss_par.wots_par.keysize, params->xmss_par.wots_par.keysize);
sig_msg += params->xmss_par.wots_par.keysize;
*sig_msg_len += params->xmss_par.wots_par.keysize;
// put AUTH nodes in place
memcpy(sig_msg, states[i].auth, tree_h*n);
sig_msg += tree_h*n;
*sig_msg_len += tree_h*n;
}
updates = (tree_h - k) >> 1;
setTreeADRS(addr, (idx_tree + 1));
// mandatory update for NEXT_0 (does not count towards h-k/2) if NEXT_0 exists
if ((1 + idx_tree) * (1 << tree_h) + idx_leaf < (1ULL << h)) {
bds_state_update(&states[params->d], sk_seed, &(params->xmss_par), pub_seed, addr);
}
for (i = 0; i < params->d; i++) {
// check if we're not at the end of a tree
if (! (((idx + 1) & ((1ULL << ((i+1)*tree_h)) - 1)) == 0)) {
idx_leaf = (idx >> (tree_h * i)) & ((1 << tree_h)-1);
idx_tree = (idx >> (tree_h * (i+1)));
setLayerADRS(addr, i);
setTreeADRS(addr, idx_tree);
if (i == (unsigned int) (needswap_upto + 1)) {
bds_round(&states[i], idx_leaf, sk_seed, &(params->xmss_par), pub_seed, addr);
}
updates = bds_treehash_update(&states[i], updates, sk_seed, &(params->xmss_par), pub_seed, addr);
setTreeADRS(addr, (idx_tree + 1));
// if a NEXT-tree exists for this level;
if ((1 + idx_tree) * (1 << tree_h) + idx_leaf < (1ULL << (h - tree_h * i))) {
if (i > 0 && updates > 0 && states[params->d + i].next_leaf < (1ULL << h)) {
bds_state_update(&states[params->d + i], sk_seed, &(params->xmss_par), pub_seed, addr);
updates--;
}
}
}
else if (idx < (1ULL << h) - 1) {
memcpy(&tmp, states+params->d + i, sizeof(bds_state));
memcpy(states+params->d + i, states + i, sizeof(bds_state));
memcpy(states + i, &tmp, sizeof(bds_state));
setLayerADRS(ots_addr, (i+1));
setTreeADRS(ots_addr, ((idx + 1) >> ((i+2) * tree_h)));
setOTSADRS(ots_addr, (((idx >> ((i+1) * tree_h)) + 1) & ((1 << tree_h)-1)));
get_seed(ots_seed, sk+params->index_len, n, ots_addr);
wots_sign(wots_sigs + i*params->xmss_par.wots_par.keysize, states[i].stack, ots_seed, &(params->xmss_par.wots_par), pub_seed, ots_addr);
states[params->d + i].stackoffset = 0;
states[params->d + i].next_leaf = 0;
updates--; // WOTS-signing counts as one update
needswap_upto = i;
for (j = 0; j < tree_h-k; j++) {
states[i].treehash[j].completed = 1;
}
}
}
//Whipe secret elements?
//zerobytes(tsk, CRYPTO_SECRETKEYBYTES);
memcpy(sig_msg, msg, msglen);
*sig_msg_len += msglen;
return 0;
}
/**
* Verifies a given message signature pair under a given public key.
*/
int xmssmt_sign_open(unsigned char *msg, unsigned long long *msglen, const unsigned char *sig_msg, unsigned long long sig_msg_len, const unsigned char *pk, const xmssmt_params *params)
{
unsigned int n = params->n;
unsigned int tree_h = params->xmss_par.h;
unsigned int idx_len = params->index_len;
uint64_t idx_tree;
uint32_t idx_leaf;
unsigned long long i, m_len;
unsigned long long idx=0;
unsigned char wots_pk[params->xmss_par.wots_par.keysize];
unsigned char pkhash[n];
unsigned char root[n];
unsigned char msg_h[n];
unsigned char hash_key[3*n];
unsigned char pub_seed[n];
memcpy(pub_seed, pk+n, n);
// Init addresses
uint32_t ots_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
uint32_t ltree_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
uint32_t node_addr[8] = {0, 0, 0, 0, 0, 0, 0, 0};
// Extract index
for (i = 0; i < idx_len; i++) {
idx |= ((unsigned long long)sig_msg[i]) << (8*(idx_len - 1 - i));
}
printf("verify:: idx = %llu\n", idx);
sig_msg += idx_len;
sig_msg_len -= idx_len;
// Generate hash key (R || root || idx)
memcpy(hash_key, sig_msg,n);
memcpy(hash_key+n, pk, n);
to_byte(hash_key+2*n, idx, n);
sig_msg += n;
sig_msg_len -= n;
// hash message (recall, R is now on pole position at sig_msg
unsigned long long tmp_sig_len = (params->d * params->xmss_par.wots_par.keysize) + (params->h * n);
m_len = sig_msg_len - tmp_sig_len;
h_msg(msg_h, sig_msg + tmp_sig_len, m_len, hash_key, 3*n, n);
//-----------------------
// Verify signature
//-----------------------
// Prepare Address
idx_tree = idx >> tree_h;
idx_leaf = (idx & ((1 << tree_h)-1));
setLayerADRS(ots_addr, 0);
setTreeADRS(ots_addr, idx_tree);
setType(ots_addr, 0);
memcpy(ltree_addr, ots_addr, 12);
setType(ltree_addr, 1);
memcpy(node_addr, ltree_addr, 12);
setType(node_addr, 2);
setOTSADRS(ots_addr, idx_leaf);
// Check WOTS signature
wots_pkFromSig(wots_pk, sig_msg, msg_h, &(params->xmss_par.wots_par), pub_seed, ots_addr);
sig_msg += params->xmss_par.wots_par.keysize;
sig_msg_len -= params->xmss_par.wots_par.keysize;
// Compute Ltree
setLtreeADRS(ltree_addr, idx_leaf);
l_tree(pkhash, wots_pk, &(params->xmss_par), pub_seed, ltree_addr);
// Compute root
validate_authpath(root, pkhash, idx_leaf, sig_msg, &(params->xmss_par), pub_seed, node_addr);
sig_msg += tree_h*n;
sig_msg_len -= tree_h*n;
for (i = 1; i < params->d; i++) {
// Prepare Address
idx_leaf = (idx_tree & ((1 << tree_h)-1));
idx_tree = idx_tree >> tree_h;
setLayerADRS(ots_addr, i);
setTreeADRS(ots_addr, idx_tree);
setType(ots_addr, 0);
memcpy(ltree_addr, ots_addr, 12);
setType(ltree_addr, 1);
memcpy(node_addr, ltree_addr, 12);
setType(node_addr, 2);
setOTSADRS(ots_addr, idx_leaf);
// Check WOTS signature
wots_pkFromSig(wots_pk, sig_msg, root, &(params->xmss_par.wots_par), pub_seed, ots_addr);
sig_msg += params->xmss_par.wots_par.keysize;
sig_msg_len -= params->xmss_par.wots_par.keysize;
// Compute Ltree
setLtreeADRS(ltree_addr, idx_leaf);
l_tree(pkhash, wots_pk, &(params->xmss_par), pub_seed, ltree_addr);
// Compute root
validate_authpath(root, pkhash, idx_leaf, sig_msg, &(params->xmss_par), pub_seed, node_addr);
sig_msg += tree_h*n;
sig_msg_len -= tree_h*n;
}
for (i = 0; i < n; i++)
if (root[i] != pk[i])
goto fail;
*msglen = sig_msg_len;
for (i = 0; i < *msglen; i++)
msg[i] = sig_msg[i];
return 0;
fail:
*msglen = sig_msg_len;
for (i = 0; i < *msglen; i++)
msg[i] = 0;
*msglen = -1;
return -1;
}
#endif /* WITH_XMSS */