155 lines
3.9 KiB
C
155 lines
3.9 KiB
C
/*
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wots.c version 20160722
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Andreas Hülsing
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Joost Rijneveld
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Public domain.
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*/
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#include <stdint.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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#include "hash_address.h"
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#include "params.h"
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/**
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* Helper method for pseudorandom key generation
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* Expands an n-byte array into a len*n byte array
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* this is done using PRF
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*/
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static void expand_seed(unsigned char *outseeds, const unsigned char *inseed)
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{
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uint32_t i;
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unsigned char ctr[32];
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for (i = 0; i < XMSS_WOTS_LEN; i++) {
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to_byte(ctr, i, 32);
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prf(outseeds + i*XMSS_N, ctr, inseed, XMSS_N);
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}
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}
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/**
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* Computes the chaining function.
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* out and in have to be n-byte arrays
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*
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* interpretes in as start-th value of the chain
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* addr has to contain the address of the chain
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*/
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static void gen_chain(unsigned char *out, const unsigned char *in,
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unsigned int start, unsigned int steps,
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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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for (i = 0; i < XMSS_N; i++) {
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out[i] = in[i];
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}
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for (i = start; i < (start+steps) && i < XMSS_WOTS_W; i++) {
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set_hash_addr(addr, i);
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hash_f(out, out, pub_seed, addr);
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}
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}
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/**
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* base_w algorithm as described in draft.
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*/
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static void base_w(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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int bits = 0;
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int i;
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for (i = 0; i < out_len; i++) {
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if (bits == 0) {
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total = input[in];
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in++;
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bits += 8;
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}
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bits -= XMSS_WOTS_LOG_W;
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output[out] = (total >> bits) & (XMSS_WOTS_W - 1);
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out++;
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}
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}
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void wots_pkgen(unsigned char *pk, const unsigned char *sk,
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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(pk, sk);
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for (i = 0; i < XMSS_WOTS_LEN; i++) {
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set_chain_addr(addr, i);
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gen_chain(pk + i*XMSS_N, pk + i*XMSS_N,
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0, XMSS_WOTS_W-1, pub_seed, addr);
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}
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}
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void wots_sign(unsigned char *sig, const unsigned char *msg,
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const unsigned char *sk, const unsigned char *pub_seed,
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uint32_t addr[8])
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{
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int basew[XMSS_WOTS_LEN];
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int csum = 0;
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unsigned char csum_bytes[((XMSS_WOTS_LEN2 * XMSS_WOTS_LOG_W) + 7) / 8];
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int csum_basew[XMSS_WOTS_LEN2];
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uint32_t i;
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base_w(basew, XMSS_WOTS_LEN1, msg);
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for (i = 0; i < XMSS_WOTS_LEN1; i++) {
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csum += XMSS_WOTS_W - 1 - basew[i];
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}
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csum = csum << (8 - ((XMSS_WOTS_LEN2 * XMSS_WOTS_LOG_W) % 8));
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to_byte(csum_bytes, csum, ((XMSS_WOTS_LEN2 * XMSS_WOTS_LOG_W) + 7) / 8);
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base_w(csum_basew, XMSS_WOTS_LEN2, csum_bytes);
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for (i = 0; i < XMSS_WOTS_LEN2; i++) {
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basew[XMSS_WOTS_LEN1 + i] = csum_basew[i];
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}
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expand_seed(sig, sk);
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for (i = 0; i < XMSS_WOTS_LEN; i++) {
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set_chain_addr(addr, i);
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gen_chain(sig + i*XMSS_N, sig + i*XMSS_N,
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0, basew[i], pub_seed, addr);
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}
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}
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void wots_pk_from_sig(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[XMSS_WOTS_LEN];
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int csum = 0;
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unsigned char csum_bytes[((XMSS_WOTS_LEN2 * XMSS_WOTS_LOG_W) + 7) / 8];
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int csum_basew[XMSS_WOTS_LEN2];
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uint32_t i = 0;
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base_w(basew, XMSS_WOTS_LEN1, msg);
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for (i=0; i < XMSS_WOTS_LEN1; i++) {
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csum += XMSS_WOTS_W - 1 - basew[i];
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}
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csum = csum << (8 - ((XMSS_WOTS_LEN2 * XMSS_WOTS_LOG_W) % 8));
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to_byte(csum_bytes, csum, ((XMSS_WOTS_LEN2 * XMSS_WOTS_LOG_W) + 7) / 8);
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base_w(csum_basew, XMSS_WOTS_LEN2, csum_bytes);
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for (i = 0; i < XMSS_WOTS_LEN2; i++) {
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basew[XMSS_WOTS_LEN1 + i] = csum_basew[i];
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}
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for (i=0; i < XMSS_WOTS_LEN; i++) {
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set_chain_addr(addr, i);
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gen_chain(pk + i*XMSS_N, sig + i*XMSS_N,
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basew[i], XMSS_WOTS_W-1-basew[i], pub_seed, addr);
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}
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}
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