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common: add blinding helpers.

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We'll want this once we add blinded HTLCs.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell
2020-04-03 13:46:56 +10:30
parent d9fc99ea39
commit 91251b1870
7 changed files with 78 additions and 84 deletions
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2
devtools/Makefile
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@@ -70,7 +70,7 @@ devtools/onion.c: ccan/config.h
devtools/onion: $(DEVTOOLS_OBJS) $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS) $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o devtools/onion.o common/sphinx.o
devtools/blindedpath: $(DEVTOOLS_OBJS) $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS) $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o devtools/blindedpath.o common/sphinx.o
devtools/blindedpath: $(DEVTOOLS_OBJS) $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS) common/blinding.o $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o devtools/blindedpath.o common/sphinx.o
devtools/gossipwith: $(DEVTOOLS_OBJS) $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(CCAN_OBJS) $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o wire/gen_peer_wire.o devtools/gossipwith.o common/cryptomsg.o common/cryptomsg.o common/crypto_sync.o

57
devtools/blindedpath.c
View File

@@ -6,6 +6,7 @@
#include <ccan/opt/opt.h>
#include <ccan/str/hex/hex.h>
#include <ccan/tal/tal.h>
#include <common/blinding.h>
#include <common/hmac.h>
#include <common/sphinx.h>
#include <common/type_to_string.h>
@@ -40,51 +41,6 @@ static void tal_freefn(void *ptr)
tal_free(ptr);
}
/* E(i-1) = H(E(i) || ss(i)) * E(i) */
static struct sha256 hash_e_and_ss(const struct pubkey *e,
const struct secret *ss)
{
u8 der[PUBKEY_CMPR_LEN];
struct sha256_ctx shactx;
struct sha256 h;
pubkey_to_der(der, e);
sha256_init(&shactx);
sha256_update(&shactx, der, sizeof(der));
sha256_update(&shactx, ss->data, sizeof(ss->data));
sha256_done(&shactx, &h);
return h;
}
/* E(i-1) = H(E(i) || ss(i)) * E(i) */
static struct pubkey next_pubkey(const struct pubkey *pk,
const struct sha256 *h)
{
struct pubkey ret;
ret = *pk;
if (secp256k1_ec_pubkey_tweak_mul(secp256k1_ctx, &ret.pubkey, h->u.u8)
!= 1)
abort();
return ret;
}
/* e(i+1) = H(E(i) || ss(i)) * e(i) */
static struct privkey next_privkey(const struct privkey *e,
const struct sha256 *h)
{
struct privkey ret;
ret = *e;
if (secp256k1_ec_privkey_tweak_mul(secp256k1_ctx, ret.secret.data,
h->u.u8) != 1)
abort();
return ret;
}
int main(int argc, char **argv)
{
bool first = false;
@@ -155,10 +111,11 @@ int main(int argc, char **argv)
abort();
}
subkey_from_hmac("rho", &ss, &rho[i]);
h = hash_e_and_ss(&pk_e[i], &ss);
blinding_hash_e_and_ss(&pk_e[i], &ss, &h);
if (i != num-1)
pk_e[i+1] = next_pubkey(&pk_e[i], &h);
e = next_privkey(&e, &h);
blinding_next_pubkey(&pk_e[i], &h,
&pk_e[i+1]);
blinding_next_privkey(&e, &h, &e);
}
/* Print initial blinding factor */
@@ -326,8 +283,8 @@ int main(int argc, char **argv)
printf("Contents: %s\n", tal_hex(tmpctx, dec));
/* E(i-1) = H(E(i) || ss(i)) * E(i) */
h = hash_e_and_ss(&blinding, &ss);
res = next_pubkey(&blinding, &h);
blinding_hash_e_and_ss(&blinding, &ss, &h);
blinding_next_pubkey(&blinding, &h, &res);
printf("Next blinding: %s\n",
type_to_string(tmpctx, struct pubkey, &res));
printf("Next onion: %s\n", tal_hex(tmpctx, serialize_onionpacket(tmpctx, rs->next)));