Annotation of src/usr.bin/ssh/xmss_wots.c, Revision 1.2
1.2 ! dtucker 1: /* $OpenBSD$ */
1.1 markus 2: /*
3: wots.c version 20160722
4: Andreas Hülsing
5: Joost Rijneveld
6: Public domain.
7: */
8:
9: #include <stdlib.h>
10: #include <stdint.h>
11: #include <limits.h>
12: #include "xmss_commons.h"
13: #include "xmss_hash.h"
14: #include "xmss_wots.h"
15: #include "xmss_hash_address.h"
16:
17:
18: /* libm-free version of log2() for wots */
19: static inline int
20: wots_log2(uint32_t v)
21: {
22: int b;
23:
24: for (b = sizeof (v) * CHAR_BIT - 1; b >= 0; b--) {
25: if ((1U << b) & v) {
26: return b;
27: }
28: }
29: return 0;
30: }
31:
32: void
33: wots_set_params(wots_params *params, int n, int w)
34: {
35: params->n = n;
36: params->w = w;
37: params->log_w = wots_log2(params->w);
38: params->len_1 = (CHAR_BIT * n) / params->log_w;
39: params->len_2 = (wots_log2(params->len_1 * (w - 1)) / params->log_w) + 1;
40: params->len = params->len_1 + params->len_2;
41: params->keysize = params->len * params->n;
42: }
43:
44: /**
45: * Helper method for pseudorandom key generation
46: * Expands an n-byte array into a len*n byte array
47: * this is done using PRF
48: */
49: static void expand_seed(unsigned char *outseeds, const unsigned char *inseed, const wots_params *params)
50: {
51: uint32_t i = 0;
52: unsigned char ctr[32];
53: for(i = 0; i < params->len; i++){
54: to_byte(ctr, i, 32);
55: prf((outseeds + (i*params->n)), ctr, inseed, params->n);
56: }
57: }
58:
59: /**
60: * Computes the chaining function.
61: * out and in have to be n-byte arrays
62: *
63: * interpretes in as start-th value of the chain
64: * addr has to contain the address of the chain
65: */
66: static void gen_chain(unsigned char *out, const unsigned char *in, unsigned int start, unsigned int steps, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
67: {
68: uint32_t i, j;
69: for (j = 0; j < params->n; j++)
70: out[j] = in[j];
71:
72: for (i = start; i < (start+steps) && i < params->w; i++) {
73: setHashADRS(addr, i);
74: hash_f(out, out, pub_seed, addr, params->n);
75: }
76: }
77:
78: /**
79: * base_w algorithm as described in draft.
80: *
81: *
82: */
83: static void base_w(int *output, const int out_len, const unsigned char *input, const wots_params *params)
84: {
85: int in = 0;
86: int out = 0;
87: uint32_t total = 0;
88: int bits = 0;
89: int consumed = 0;
90:
91: for (consumed = 0; consumed < out_len; consumed++) {
92: if (bits == 0) {
93: total = input[in];
94: in++;
95: bits += 8;
96: }
97: bits -= params->log_w;
98: output[out] = (total >> bits) & (params->w - 1);
99: out++;
100: }
101: }
102:
103: void wots_pkgen(unsigned char *pk, const unsigned char *sk, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
104: {
105: uint32_t i;
106: expand_seed(pk, sk, params);
107: for (i=0; i < params->len; i++) {
108: setChainADRS(addr, i);
109: gen_chain(pk+i*params->n, pk+i*params->n, 0, params->w-1, params, pub_seed, addr);
110: }
111: }
112:
113:
114: int wots_sign(unsigned char *sig, const unsigned char *msg, const unsigned char *sk, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
115: {
116: //int basew[params->len];
117: int csum = 0;
118: uint32_t i = 0;
119: int *basew = calloc(params->len, sizeof(int));
120: if (basew == NULL)
121: return -1;
122:
123: base_w(basew, params->len_1, msg, params);
124:
125: for (i=0; i < params->len_1; i++) {
126: csum += params->w - 1 - basew[i];
127: }
128:
129: csum = csum << (8 - ((params->len_2 * params->log_w) % 8));
130:
131: int len_2_bytes = ((params->len_2 * params->log_w) + 7) / 8;
132:
133: unsigned char csum_bytes[len_2_bytes];
134: to_byte(csum_bytes, csum, len_2_bytes);
135:
136: int csum_basew[params->len_2];
137: base_w(csum_basew, params->len_2, csum_bytes, params);
138:
139: for (i = 0; i < params->len_2; i++) {
140: basew[params->len_1 + i] = csum_basew[i];
141: }
142:
143: expand_seed(sig, sk, params);
144:
145: for (i = 0; i < params->len; i++) {
146: setChainADRS(addr, i);
147: gen_chain(sig+i*params->n, sig+i*params->n, 0, basew[i], params, pub_seed, addr);
148: }
149: free(basew);
150: return 0;
151: }
152:
153: int wots_pkFromSig(unsigned char *pk, const unsigned char *sig, const unsigned char *msg, const wots_params *params, const unsigned char *pub_seed, uint32_t addr[8])
154: {
155: int csum = 0;
156: uint32_t i = 0;
157: int *basew = calloc(params->len, sizeof(int));
158: if (basew == NULL)
159: return -1;
160:
161: base_w(basew, params->len_1, msg, params);
162:
163: for (i=0; i < params->len_1; i++) {
164: csum += params->w - 1 - basew[i];
165: }
166:
167: csum = csum << (8 - ((params->len_2 * params->log_w) % 8));
168:
169: int len_2_bytes = ((params->len_2 * params->log_w) + 7) / 8;
170:
171: unsigned char csum_bytes[len_2_bytes];
172: to_byte(csum_bytes, csum, len_2_bytes);
173:
174: int csum_basew[params->len_2];
175: base_w(csum_basew, params->len_2, csum_bytes, params);
176:
177: for (i = 0; i < params->len_2; i++) {
178: basew[params->len_1 + i] = csum_basew[i];
179: }
180: for (i=0; i < params->len; i++) {
181: setChainADRS(addr, i);
182: gen_chain(pk+i*params->n, sig+i*params->n, basew[i], params->w-1-basew[i], params, pub_seed, addr);
183: }
184: free(basew);
185: return 0;
186: }
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