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surjectionproof: introduce SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS constant and set it to 16

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This commit is contained in:
Andrew Poelstra 2019-04-30 23:04:08 +00:00
parent a118acc02b
commit d512d78653
4 changed files with 19 additions and 12 deletions
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10
include/secp256k1_surjectionproof.h
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@ -11,6 +11,9 @@ extern "C" {
/** Maximum number of inputs that may be given in a surjection proof */
#define SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS 256
/** Maximum number of inputs that may be used in a surjection proof */
#define SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS 16
/** Number of bytes a serialized surjection proof requires given the
* number of inputs and the number of used inputs.
*/
@ -19,7 +22,7 @@ extern "C" {
/** Maximum number of bytes a serialized surjection proof requires. */
#define SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES_MAX \
SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES(SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS, SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS)
SECP256K1_SURJECTIONPROOF_SERIALIZATION_BYTES(SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS, SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS)
/** Opaque data structure that holds a parsed surjection proof
*
@ -46,7 +49,7 @@ typedef struct {
/** Bitmap of which input tags are used in the surjection proof */
unsigned char used_inputs[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS / 8];
/** Borromean signature: e0, scalars */
unsigned char data[32 * (1 + SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS)];
unsigned char data[32 * (1 + SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS)];
} secp256k1_surjectionproof;
/** Parse a surjection proof
@ -143,7 +146,8 @@ SECP256K1_API size_t secp256k1_surjectionproof_serialized_size(
* e.g. in a coinjoin with others' inputs, an ephemeral tag can be given;
* this won't match the output tag but might be used in the anonymity set.)
* n_input_tags: the number of entries in the fixed_input_tags array
* n_input_tags_to_use: the number of inputs to select randomly to put in the anonymity set
* n_input_tags_to_use: the number of inputs to select randomly to put in the anonymity set
* Must be <= SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS
* fixed_output_tag: fixed output tag
* max_n_iterations: the maximum number of iterations to do before giving up. Because the
* maximum number of inputs (SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS) is

17
src/modules/surjection/main_impl.h
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@ -9,11 +9,12 @@
#include <assert.h>
#include <string.h>
#include "include/secp256k1_rangeproof.h"
#include "include/secp256k1_surjectionproof.h"
#include "modules/rangeproof/borromean.h"
#include "modules/surjection/surjection_impl.h"
#include "hash.h"
#include "include/secp256k1_rangeproof.h"
#include "include/secp256k1_surjectionproof.h"
static size_t secp256k1_count_bits_set(const unsigned char* data, size_t count) {
size_t ret = 0;
@ -270,8 +271,8 @@ int secp256k1_surjectionproof_generate(const secp256k1_context* ctx, secp256k1_s
size_t n_total_pubkeys;
size_t n_used_pubkeys;
size_t ring_input_index = 0;
secp256k1_gej ring_pubkeys[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
secp256k1_scalar borromean_s[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
secp256k1_gej ring_pubkeys[SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS];
secp256k1_scalar borromean_s[SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS];
unsigned char msg32[32];
VERIFY_CHECK(ctx != NULL);
@ -310,7 +311,9 @@ int secp256k1_surjectionproof_generate(const secp256k1_context* ctx, secp256k1_s
return 0;
}
secp256k1_surjection_compute_public_keys(ring_pubkeys, n_used_pubkeys, ephemeral_input_tags, n_total_pubkeys, proof->used_inputs, ephemeral_output_tag, input_index, &ring_input_index);
if (secp256k1_surjection_compute_public_keys(ring_pubkeys, n_used_pubkeys, ephemeral_input_tags, n_total_pubkeys, proof->used_inputs, ephemeral_output_tag, input_index, &ring_input_index) == 0) {
return 0;
}
/* Produce signature */
rsizes[0] = (int) n_used_pubkeys;
@ -338,8 +341,8 @@ int secp256k1_surjectionproof_verify(const secp256k1_context* ctx, const secp256
size_t i;
size_t n_total_pubkeys;
size_t n_used_pubkeys;
secp256k1_gej ring_pubkeys[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
secp256k1_scalar borromean_s[SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS];
secp256k1_gej ring_pubkeys[SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS];
secp256k1_scalar borromean_s[SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS];
unsigned char msg32[32];
VERIFY_CHECK(ctx != NULL);

2
src/modules/surjection/surjection_impl.h
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@ -77,7 +77,7 @@ SECP256K1_INLINE static int secp256k1_surjection_compute_public_keys(secp256k1_g
*ring_input_index = j;
}
j++;
if (j > n_pubkeys) {
if (j > n_pubkeys || j > SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS) {
return 0;
}
}

2
src/modules/surjection/tests_impl.h
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@ -671,7 +671,7 @@ void run_surjection_tests(void) {
test_input_selection_distribution();
test_gen_verify(10, 3);
test_gen_verify(SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS, SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS);
test_gen_verify(SECP256K1_SURJECTIONPROOF_MAX_N_INPUTS, SECP256K1_SURJECTIONPROOF_MAX_USED_INPUTS);
test_no_used_inputs_verify();
test_bad_serialize();
test_bad_parse();