Refactor and deduplicate WOTS
This commit is contained in:
Joost Rijneveld
förälder
c4d4e93bbd
incheckning
cd8e621dac
121
wots.c
121
wots.c
@ -1,4 +1,6 @@
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#include <stdint.h>
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#include <string.h>
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#include "xmss_commons.h"
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#include "hash.h"
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#include "wots.h"
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@ -35,10 +37,10 @@ static void gen_chain(const xmss_params *params,
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{
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uint32_t i;
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for (i = 0; i < params->n; i++) {
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out[i] = in[i];
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}
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/* Initialize out with the value at position 'start'. */
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memcpy(out, in, params->n);
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/* Iterate 'steps' calls to the hash function. */
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for (i = start; i < (start+steps) && i < params->wots_w; i++) {
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set_hash_addr(addr, i);
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hash_f(params, out, out, pub_seed, addr);
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@ -48,17 +50,18 @@ static void gen_chain(const xmss_params *params,
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/**
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* base_w algorithm as described in draft.
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* Interprets an array of bytes as integers in base w.
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* This only works when log_w is a divisor of 8.
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*/
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static void base_w(const xmss_params *params,
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int *output, const int out_len, const unsigned char *input)
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{
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int in = 0;
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int out = 0;
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uint8_t total = 0;
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unsigned char total;
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int bits = 0;
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int i;
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int consumed;
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for (i = 0; i < out_len; i++) {
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for (consumed = 0; consumed < out_len; consumed++) {
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if (bits == 0) {
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total = input[in];
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in++;
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@ -70,83 +73,99 @@ static void base_w(const xmss_params *params,
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}
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}
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/* Computes the WOTS+ checksum over a message (in base_w). */
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static void wots_checksum(const xmss_params *params,
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int *csum_base_w, const int *msg_base_w)
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{
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int csum = 0;
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unsigned char csum_bytes[(params->wots_len2 * params->wots_log_w + 7) / 8];
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unsigned int i;
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/* Compute checksum. */
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for (i = 0; i < params->wots_len1; i++) {
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csum += params->wots_w - 1 - msg_base_w[i];
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}
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/* Convert checksum to base_w. */
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/* Make sure expected empty zero bits are the least significant bits. */
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csum = csum << (8 - ((params->wots_len2 * params->wots_log_w) % 8));
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ull_to_bytes(csum_bytes, csum, sizeof(csum_bytes));
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base_w(params, csum_base_w, params->wots_len2, csum_bytes);
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}
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/* Takes a message and derives the matching chain lengths. */
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static void chain_lengths(const xmss_params *params,
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int *lengths, const unsigned char *msg)
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{
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base_w(params, lengths, params->wots_len1, msg);
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wots_checksum(params, lengths + params->wots_len1, lengths);
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}
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/**
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* WOTS key generation. Takes a 32 byte seed for the private key, expands it to
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* a full WOTS private key and computes the corresponding public key.
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* It requires the seed pub_seed (used to generate bitmasks and hash keys)
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* and the address of this WOTS key pair.
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*
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* Writes the computed public key to 'pk'.
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*/
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void wots_pkgen(const xmss_params *params,
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unsigned char *pk, const unsigned char *sk,
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unsigned char *pk, const unsigned char *seed,
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const unsigned char *pub_seed, uint32_t addr[8])
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{
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uint32_t i;
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expand_seed(params, pk, sk);
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/* The WOTS+ private key is derived from the seed. */
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expand_seed(params, pk, seed);
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for (i = 0; i < params->wots_len; i++) {
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set_chain_addr(addr, i);
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gen_chain(params, pk + i*params->n, pk + i*params->n,
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0, params->wots_w-1, pub_seed, addr);
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0, params->wots_w - 1, pub_seed, addr);
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}
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}
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/**
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* Takes a m-byte message and the 32-byte seed for the private key to compute a
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* signature that is placed at 'sig'.
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*/
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void wots_sign(const xmss_params *params,
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unsigned char *sig, const unsigned char *msg,
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const unsigned char *sk, const unsigned char *pub_seed,
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const unsigned char *seed, const unsigned char *pub_seed,
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uint32_t addr[8])
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{
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int basew[params->wots_len];
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int csum = 0;
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unsigned char csum_bytes[((params->wots_len2 * params->wots_log_w) + 7) / 8];
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int csum_basew[params->wots_len2];
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int lengths[params->wots_len];
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uint32_t i;
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base_w(params, basew, params->wots_len1, msg);
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chain_lengths(params, lengths, msg);
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for (i = 0; i < params->wots_len1; i++) {
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csum += params->wots_w - 1 - basew[i];
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}
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csum = csum << (8 - ((params->wots_len2 * params->wots_log_w) % 8));
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ull_to_bytes(csum_bytes, csum, ((params->wots_len2 * params->wots_log_w) + 7) / 8);
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base_w(params, csum_basew, params->wots_len2, csum_bytes);
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for (i = 0; i < params->wots_len2; i++) {
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basew[params->wots_len1 + i] = csum_basew[i];
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}
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expand_seed(params, sig, sk);
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/* The WOTS+ private key is derived from the seed. */
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expand_seed(params, sig, seed);
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for (i = 0; i < params->wots_len; i++) {
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set_chain_addr(addr, i);
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gen_chain(params, sig + i*params->n, sig + i*params->n,
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0, basew[i], pub_seed, addr);
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0, lengths[i], pub_seed, addr);
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}
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}
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/**
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* Takes a WOTS signature and an m-byte message, computes a WOTS public key.
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*
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* Writes the computed public key to 'pk'.
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*/
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void wots_pk_from_sig(const xmss_params *params, unsigned char *pk,
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const unsigned char *sig, const unsigned char *msg,
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const unsigned char *pub_seed, uint32_t addr[8])
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{
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int basew[params->wots_len];
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int csum = 0;
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unsigned char csum_bytes[((params->wots_len2 * params->wots_log_w) + 7) / 8];
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int csum_basew[params->wots_len2];
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uint32_t i = 0;
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int lengths[params->wots_len];
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uint32_t i;
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base_w(params, basew, params->wots_len1, msg);
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chain_lengths(params, lengths, msg);
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for (i=0; i < params->wots_len1; i++) {
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csum += params->wots_w - 1 - basew[i];
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}
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csum = csum << (8 - ((params->wots_len2 * params->wots_log_w) % 8));
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ull_to_bytes(csum_bytes, csum, ((params->wots_len2 * params->wots_log_w) + 7) / 8);
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base_w(params, csum_basew, params->wots_len2, csum_bytes);
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for (i = 0; i < params->wots_len2; i++) {
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basew[params->wots_len1 + i] = csum_basew[i];
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}
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for (i=0; i < params->wots_len; i++) {
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for (i = 0; i < params->wots_len; i++) {
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set_chain_addr(addr, i);
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gen_chain(params, pk + i*params->n, sig + i*params->n,
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basew[i], params->wots_w-1-basew[i], pub_seed, addr);
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lengths[i], params->wots_w - 1 - lengths[i], pub_seed, addr);
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}
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}
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10
wots.h
10
wots.h
@ -5,24 +5,24 @@
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#include "params.h"
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/**
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* WOTS key generation. Takes a 32 byte seed for the secret key, expands it to
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* a full WOTS secret key and computes the corresponding public key.
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* WOTS key generation. Takes a 32 byte seed for the private key, expands it to
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* a full WOTS private key and computes the corresponding public key.
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* It requires the seed pub_seed (used to generate bitmasks and hash keys)
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* and the address of this WOTS key pair.
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*
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* Writes the computed public key to 'pk'.
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*/
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void wots_pkgen(const xmss_params *params,
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unsigned char *pk, const unsigned char *sk,
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unsigned char *pk, const unsigned char *seed,
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const unsigned char *pub_seed, uint32_t addr[8]);
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/**
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* Takes a m-byte message and the 32-byte seed for the secret key to compute a
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* Takes a m-byte message and the 32-byte seed for the private key to compute a
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* signature that is placed at 'sig'.
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*/
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void wots_sign(const xmss_params *params,
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unsigned char *sig, const unsigned char *msg,
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const unsigned char *sk, const unsigned char *pub_seed,
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const unsigned char *seed, const unsigned char *pub_seed,
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uint32_t addr[8]);
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/**
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