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// SPDX-License-Identifier: MIT
/*
* This is the code that implements the tree part of the LMS hash
* based signatures
*/
#include <string.h>
#include "lm_common.h"
#include "hash.h"
#include "common_defs.h"
#include "lm_ots_common.h"
/*
* Internal utility to convert encoded parameter sets into what they represent
*/
bool lm_look_up_parameter_set(param_set_t parameter_set,
unsigned *h, unsigned *n, unsigned *height) {
unsigned v_h, v_n, v_height;
switch (parameter_set) {
case LMS_SHA256_N32_H5:
v_h = HASH_SHA256; v_n = 32; v_height = 5; break;
case LMS_SHA256_N32_H10:
v_h = HASH_SHA256; v_n = 32; v_height = 10; break;
case LMS_SHA256_N32_H15:
v_h = HASH_SHA256; v_n = 32; v_height = 15; break;
case LMS_SHA256_N32_H20:
v_h = HASH_SHA256; v_n = 32; v_height = 20; break;
case LMS_SHA256_N32_H25:
v_h = HASH_SHA256; v_n = 32; v_height = 25; break;
default: return false;
}
if (h) *h = v_h;
if (n) *n = v_n;
if (height) *height = v_height;
return true;
}
/* The LM public key consists of: */
#define LM_PUB_PARM_SET 0 /* The parameter set (4 bytes) */
#define LM_PUB_OTS_PARM_SET 4 /* The OTS parameter set (4 bytes) */
#define LM_PUB_I 8 /* Our nonce (I) value (16 bytes) */
/* The root value comes here */
/*
* XDR requires us to pad the I value out to a multiple of 4
* This computes how long the field will be after padding
* That is, it rounds len_I up to the next multiple of 4
*/
#define padded_length(len_I) (((len_I) + 3) & ~3)
/* The public key just consists of the parameter sets, plus I, plus root hash */
size_t lm_get_public_key_len(param_set_t lm_type) {
unsigned n;
if (!lm_look_up_parameter_set( lm_type, 0, &n, 0))
return 0;
return LM_PUB_I + padded_length(I_LEN) + n;
}
/*
* The amount of space we use for signature
*/
size_t lm_get_signature_len(param_set_t lm_type,
param_set_t lm_ots_type) {
unsigned n, height;
if (!lm_look_up_parameter_set( lm_type, 0, &n, &height ))
return 0;
int ots_sig_len = (int)lm_ots_get_signature_len(lm_ots_type);
if (ots_sig_len == 0)
return 0;
/*
* The LM signature consists of the type code, the diversification factor,
* the LM-OTS signature (which includes the OTS type code), and the
* authentication path (which is an array of height hashes)
*/
return 4 + 4 + ots_sig_len + n*height;
}