524 regels
14 KiB
C
524 regels
14 KiB
C
#include "xmss.h"
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#include <stdlib.h>
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#include <string.h>
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#include <stdint.h>
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#include <math.h>
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#include "randombytes.h"
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#include "wots.h"
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#include "hash.h"
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#include "prg.h"
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#include "xmss_commons.h"
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// For testing
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#include "stdio.h"
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/**
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* Macros used to manipulate the respective fields
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* in the 16byte hash address
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*/
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#define SET_OTS_BIT(a, b) {\
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a[9] = (a[9] & 253) | (b << 1);}
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#define SET_OTS_ADDRESS(a, v) {\
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a[12] = (a[12] & 1) | ((v << 1) & 255);\
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a[11] = (v >> 7) & 255;\
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a[10] = (v >> 15) & 255;\
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a[9] = (a[9] & 254) | ((v >> 23) & 1);}
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#define ZEROISE_OTS_ADDR(a) {\
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a[12] = (a[12] & 254);\
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a[13] = 0;\
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a[14] = 0;\
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a[15] = 0;}
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#define SET_LTREE_BIT(a, b) {\
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a[9] = (a[9] & 254) | b;}
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#define SET_LTREE_ADDRESS(a, v) {\
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a[12] = v & 255;\
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a[11] = (v >> 8) & 255;\
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a[10] = (v >> 16) & 255;}
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#define SET_LTREE_TREE_HEIGHT(a, v) {\
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a[13] = (a[13] & 3) | ((v << 2) & 255);}
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#define SET_LTREE_TREE_INDEX(a, v) {\
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a[15] = (a[15] & 3) | ((v << 2) & 255);\
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a[14] = (v >> 6) & 255;\
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a[13] = (a[13] & 252) | ((v >> 14) & 3);}
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#define SET_NODE_PADDING(a) {\
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a[10] = 0;\
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a[11] = a[11] & 3;}
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#define SET_NODE_TREE_HEIGHT(a, v) {\
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a[12] = (a[12] & 3) | ((v << 2) & 255);\
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a[11] = (a[11] & 252) | ((v >> 6) & 3);}
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#define SET_NODE_TREE_INDEX(a, v) {\
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a[15] = (a[15] & 3) | ((v << 2) & 255);\
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a[14] = (v >> 6) & 255;\
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a[13] = (v >> 14) & 255;\
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a[12] = (a[12] & 252) | ((v >> 22) & 3);}
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/**
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* Used for pseudorandom keygeneration,
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* generates the seed for the WOTS keypair at address addr
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*/
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static void get_seed(unsigned char seed[32], const unsigned char *sk_seed, unsigned char addr[16])
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{
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// Make sure that chain addr, hash addr, and key bit are 0!
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ZEROISE_OTS_ADDR(addr);
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// Generate pseudorandom value
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prg_with_counter(seed, 32, sk_seed, 32, addr);
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}
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/**
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* Initialize xmss params struct
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* parameter names are the same as in the draft
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*/
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void xmss_set_params(xmss_params *params, int m, int n, int h, int w)
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{
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params->h = h;
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params->m = m;
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params->n = n;
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wots_params wots_par;
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wots_set_params(&wots_par, m, n, w);
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params->wots_par = &wots_par;
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}
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/**
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* Computes a leaf from a WOTS public key using an L-tree.
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*/
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static void l_tree(unsigned char *leaf, unsigned char *wots_pk, const xmss_params *params, const unsigned char *pub_seed, unsigned char addr[16])
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{
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uint l = params->wots_par->len;
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uint n = params->n;
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unsigned long i = 0;
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uint height = 0;
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//ADRS.setTreeHeight(0);
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SET_LTREE_TREE_HEIGHT(addr,height);
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unsigned long bound;
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while ( l > 1 )
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{
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bound = l >> 1; //floor(l / 2);
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for ( i = 0; i < bound; i = i + 1 ) {
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//ADRS.setTreeIndex(i);
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SET_LTREE_TREE_INDEX(addr,i);
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//wots_pk[i] = RAND_HASH(pk[2i], pk[2i + 1], SEED, ADRS);
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hash_2n_n(wots_pk+i*n,wots_pk+i*2*n, pub_seed, addr, n);
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}
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//if ( l % 2 == 1 ) {
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if(l&1)
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{
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//pk[floor(l / 2) + 1] = pk[l];
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memcpy(wots_pk+(l>>1)*n,wots_pk+(l-1)*n, n);
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//l = ceil(l / 2);
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l=(l>>1)+1;
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}
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else
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{
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//l = ceil(l / 2);
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l=(l>>1);
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}
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//ADRS.setTreeHeight(ADRS.getTreeHeight() + 1);
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height++;
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SET_LTREE_TREE_HEIGHT(addr,height);
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}
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//return pk[0];
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memcpy(leaf,wots_pk,n);
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}
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/**
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* 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.
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*/
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static void gen_leaf_wots(unsigned char *leaf, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, unsigned char ltree_addr[16], unsigned char ots_addr[16])
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{
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unsigned char seed[32];
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unsigned char pk[params->wots_par->keysize];
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get_seed(seed, sk_seed, ots_addr);
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wots_pkgen(pk, seed, params->wots_par, pub_seed, ots_addr);
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l_tree(leaf, pk, params, pub_seed, ltree_addr);
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}
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/**
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* Merkle's TreeHash algorithm. The address only needs to initialize the first 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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*
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*/
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static void treehash(unsigned char *node, int height, int index, const unsigned char *sk_seed, const xmss_params *params, const unsigned char *pub_seed, const unsigned char addr[16])
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{
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uint idx = index;
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uint n = params->n;
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// use three different addresses because at this point we use all three formats in parallel
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unsigned char ots_addr[16];
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unsigned char ltree_addr[16];
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unsigned char node_addr[16];
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memcpy(ots_addr, addr, 10);
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SET_OTS_BIT(ots_addr, 1);
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memcpy(ltree_addr, addr, 10);
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SET_OTS_BIT(ltree_addr, 0);
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SET_LTREE_BIT(ltree_addr, 1);
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memcpy(node_addr, ltree_addr, 10);
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SET_LTREE_BIT(node_addr, 0);
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SET_NODE_PADDING(node_addr);
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int lastnode,i;
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unsigned char stack[(height+1)*n];
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unsigned int stacklevels[height+1];
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unsigned int stackoffset=0;
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lastnode = idx+(1<<height);
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for(;idx<lastnode;idx++)
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{
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SET_LTREE_ADDRESS(ltree_addr,idx);
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SET_OTS_ADDRESS(ots_addr,idx);
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gen_leaf_wots(stack+stackoffset*n,sk_seed,params, 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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{
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SET_NODE_TREE_HEIGHT(node_addr,stacklevels[stackoffset-1]);
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SET_NODE_TREE_INDEX(node_addr, (idx >> (stacklevels[stackoffset-1]+1)));
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hash_2n_n(stack+(stackoffset-2)*n,stack+(stackoffset-2)*n, pub_seed,
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node_addr, n);
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stacklevels[stackoffset-2]++;
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stackoffset--;
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}
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}
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for(i=0;i<n;i++)
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node[i] = stack[i];
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}
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/**
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* Computes a root node given a leaf and an authapth
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*/
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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, unsigned char addr[16])
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{
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uint n = params->n;
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int i,j;
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unsigned char buffer[2*n];
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// If leafidx is odd (last bit = 1), current path element is a right child and authpath has to go to the left.
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// Otherwise, it is the other way around
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if(leafidx&1)
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{
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for(j=0;j<n;j++)
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buffer[n+j] = leaf[j];
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for(j=0;j<n;j++)
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buffer[j] = authpath[j];
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}
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else
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{
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for(j=0;j<n;j++)
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buffer[j] = leaf[j];
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for(j=0;j<n;j++)
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buffer[n+j] = authpath[j];
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}
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authpath += n;
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for(i=0;i<params->h-1;i++)
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{
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SET_NODE_TREE_HEIGHT(addr,i);
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leafidx >>= 1;
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SET_NODE_TREE_INDEX(addr, leafidx);
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if(leafidx&1)
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{
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hash_2n_n(buffer+n,buffer,pub_seed, addr, n);
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for(j=0;j<n;j++)
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buffer[j] = authpath[j];
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}
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else
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{
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hash_2n_n(buffer,buffer,pub_seed, addr, n);
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for(j=0;j<n;j++)
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buffer[j+n] = authpath[j];
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}
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authpath += n;
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}
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SET_NODE_TREE_HEIGHT(addr, (params->h-1));
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leafidx >>= 1;
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SET_NODE_TREE_INDEX(addr, leafidx);
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hash_2n_n(root,buffer,pub_seed,addr,n);
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}
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/**
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* Computes the authpath and the root. This method is using a lot of space as we build the whole tree and then select the authpath nodes.
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* For more efficient algorithms see e.g. the chapter on hash-based signatures in Bernstein, Buchmann, Dahmen. "Post-quantum Cryptography", Springer 2009.
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* It returns the authpath in "authpath" with the node on level 0 at index 0.
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*/
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static void compute_authpath_wots(unsigned char *root, unsigned char *authpath, unsigned long leaf_idx, const unsigned char *sk_seed, const xmss_params *params, unsigned char *pub_seed, unsigned char addr[16])
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{
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uint i, j, level;
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int n = params->n;
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int h = params->h;
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unsigned char tree[2*(1<<h)*n];
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unsigned char ots_addr[16];
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unsigned char ltree_addr[16];
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unsigned char node_addr[16];
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memcpy(ots_addr, addr, 10);
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SET_OTS_BIT(ots_addr, 1);
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memcpy(ltree_addr, addr, 10);
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SET_OTS_BIT(ltree_addr, 0);
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SET_LTREE_BIT(ltree_addr, 1);
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memcpy(node_addr, ltree_addr, 10);
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SET_LTREE_BIT(node_addr, 0);
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SET_NODE_PADDING(node_addr);
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// Compute all leaves
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for(i = 0; i < (1<<h); i++)
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{
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SET_LTREE_ADDRESS(ltree_addr,i);
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SET_OTS_ADDRESS(ots_addr,i);
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gen_leaf_wots(tree+((1<<h)*n + i*n), sk_seed, params, pub_seed, ltree_addr, ots_addr);
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}
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level = 0;
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// Compute tree:
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// Outer loop: For each inner layer
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for (i = (1<<h); i > 0; i>>=1)
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{
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SET_NODE_TREE_HEIGHT(node_addr, level);
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// Inner loop: for each pair of sibling nodes
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for (j = 0; j < i; j+=2)
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{
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SET_NODE_TREE_INDEX(node_addr, j>>1);
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hash_2n_n(tree + (i>>1)*n + (j>>1) * n, tree + i*n + j*n, pub_seed, node_addr, n);
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}
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level++;
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}
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// copy authpath
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for(i=0;i<h;i++)
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memcpy(authpath + i*n, tree + ((1<<h)>>i)*n + ((leaf_idx >> i) ^ 1) * n, n);
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// copy root
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memcpy(root, tree+n, 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]
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* Format pk: [root || PUB_SEED] omitting algo oid.
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*/
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int xmss_keypair(unsigned char *pk, unsigned char *sk, xmss_params *params)
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{
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uint n = params->n;
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uint m = params->m;
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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 (n byte), SK_PRF (m byte), and PUB_SEED (n byte)
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randombytes(sk+4,2*n+m);
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// Copy PUB_SEED to public key
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memcpy(pk+n, sk+4+n+m,n);
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unsigned char addr[16] = {0,0,0,0};
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// Compute root
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treehash(pk, params->h, 0, sk+4, params, sk+4+n+m, addr);
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return 0;
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}
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/**
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* Signs a message.
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* Returns
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* 1. an array containing the signature followed by the message AND
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* 2. an updated secret key!
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*
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*/
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int xmss_sign(unsigned char *sk, unsigned char *sig_msg, unsigned long long *sig_msg_len, const unsigned char *msg, unsigned long long msglen, const xmss_params *params, unsigned char* pk)
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{
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uint n = params->n;
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uint m = params->m;
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// Extract SK
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unsigned long idx = (sk[0] << 24) | (sk[1] << 16) | (sk[2] << 8) || sk[3];
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unsigned char sk_seed[n];
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memcpy(sk_seed,sk+4,n);
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unsigned char sk_prf[m];
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memcpy(sk_prf,sk+4+n,m);
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unsigned char pub_seed[n];
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memcpy(pub_seed,sk+4+n+m,n);
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// Update SK
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sk[0] = ((idx + 1) >> 24) & 255;
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sk[1] = ((idx + 1) >> 16) & 255;
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sk[2] = ((idx + 1) >> 8) & 255;
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sk[3] = (idx + 1) & 255;
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// -- Secret key for this non-forward-secure version is now updated.
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// -- A productive implementation should use a file handle instead and write the updated secret key at this point!
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// Init working params
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unsigned long long i;
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unsigned char R[m];
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unsigned char msg_h[m];
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unsigned char root[n];
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unsigned char ots_seed[n];
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unsigned char ots_addr[16] = {0,0,0,0};
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// ---------------------------------
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// Message Hashing
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// ---------------------------------
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// Message Hash:
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// First compute pseudorandom key
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prf_m(R, msg, msglen, sk_prf, m);
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// Then use it for message digest
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hash_m(msg_h, msg, msglen, R, m, m);
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// Start collecting signature
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*sig_msg_len = 0;
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// Copy index to signature
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sig_msg[0] = (idx >> 24) & 255;
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sig_msg[1] = (idx >> 16) & 255;
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sig_msg[2] = (idx >> 8) & 255;
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sig_msg[3] = idx & 255;
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sig_msg += 4;
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*sig_msg_len += 4;
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// Copy R to signature
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for(i=0; i<m; i++)
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sig_msg[i] = R[i];
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sig_msg += m;
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*sig_msg_len += m;
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// ----------------------------------
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// Now we start to "really sign"
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// ----------------------------------
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// Prepare Address
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SET_OTS_BIT(ots_addr,1);
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SET_OTS_ADDRESS(ots_addr,idx);
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// Compute seed for OTS key pair
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get_seed(ots_seed, sk_seed, ots_addr);
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// Compute WOTS signature
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wots_sign(sig_msg, msg_h, ots_seed, params->wots_par, pub_seed, ots_addr);
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sig_msg += params->wots_par->keysize;
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*sig_msg_len += params->wots_par->keysize;
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compute_authpath_wots(root, sig_msg, idx, sk_seed, params, pub_seed, ots_addr);
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sig_msg += params->h*n;
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*sig_msg_len += params->h*n;
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//DEBUG
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for(i=0;i<n;i++)
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if(root[i] != pk[i])
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printf("Different PK's %llu",i);
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//Whipe secret elements?
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//zerobytes(tsk, CRYPTO_SECRETKEYBYTES);
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memcpy(sig_msg,msg,msglen);
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*sig_msg_len += msglen;
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return 0;
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}
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/**
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* Verifies a given message signature pair under a given public key.
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*/
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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)
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{
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uint n = params->n;
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uint m = params->m;
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unsigned long long i, m_len;
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unsigned long idx=0;
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unsigned char wots_pk[params->wots_par->keysize];
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unsigned char pkhash[n];
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unsigned char root[n];
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unsigned char msg_h[m];
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unsigned char pub_seed[n];
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memcpy(pub_seed,pk+n,n);
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// Init addresses
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unsigned char ots_addr[16] = {0,0,0,0};
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unsigned char ltree_addr[16];
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unsigned char node_addr[16];
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SET_OTS_BIT(ots_addr, 1);
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memcpy(ltree_addr, ots_addr, 10);
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SET_OTS_BIT(ltree_addr, 0);
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SET_LTREE_BIT(ltree_addr, 1);
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memcpy(node_addr, ltree_addr, 10);
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SET_LTREE_BIT(node_addr, 0);
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SET_NODE_PADDING(node_addr);
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// Extract index
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idx = (sig_msg[0] << 24) | (sig_msg[1] << 16) | (sig_msg[2] << 8) || sig_msg[3];
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sig_msg += 4;
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sig_msg_len -= 4;
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// hash message (recall, R is now on pole position at sig_msg
|
|
unsigned long long tmp_sig_len = m+params->wots_par->keysize+params->h*n;
|
|
m_len = sig_msg_len - tmp_sig_len;
|
|
hash_m(msg_h, sig_msg + tmp_sig_len, m_len, sig_msg, m, m);
|
|
|
|
sig_msg += m;
|
|
sig_msg_len -= m;
|
|
|
|
//-----------------------
|
|
// Verify signature
|
|
//-----------------------
|
|
|
|
// Prepare Address
|
|
SET_OTS_ADDRESS(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
|
|
SET_LTREE_ADDRESS(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;
|
|
} |