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264 lines
9.1 KiB
264 lines
9.1 KiB
#include <bitcoin/privkey.h>
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#include <bitcoin/pubkey.h>
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#include <ccan/crypto/sha256/sha256.h>
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#include <common/key_derive.h>
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#include <common/utils.h>
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#include <wally_bip32.h>
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/* BOLT #3:
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*
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* ### `localpubkey`, `remotepubkey`, `local_htlcpubkey`, `remote_htlcpubkey`, `local_delayedpubkey`, and `remote_delayedpubkey` Derivation
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*
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* These pubkeys are simply generated by addition from their base points:
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*
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* pubkey = basepoint + SHA256(per_commitment_point || basepoint) * G
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*
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* The `localpubkey` uses the local node's `payment_basepoint`; the
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* `remotepubkey` uses the remote node's `payment_basepoint`; the
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* `local_delayedpubkey` uses the local node's `delayed_payment_basepoint`; the
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* `local_htlcpubkey` uses the local node's `htlc_basepoint`; and the
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* `remote_delayedpubkey` uses the remote node's `delayed_payment_basepoint`.
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*/
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bool derive_simple_key(const struct pubkey *basepoint,
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const struct pubkey *per_commitment_point,
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struct pubkey *key)
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{
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struct sha256 sha;
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unsigned char der_keys[PUBKEY_DER_LEN * 2];
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pubkey_to_der(der_keys, per_commitment_point);
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pubkey_to_der(der_keys + PUBKEY_DER_LEN, basepoint);
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sha256(&sha, der_keys, sizeof(der_keys));
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#ifdef SUPERVERBOSE
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printf("# SHA256(per_commitment_point || basepoint)\n");
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printf("# => SHA256(0x%s || 0x%s)\n",
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tal_hexstr(tmpctx, der_keys, PUBKEY_DER_LEN),
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tal_hexstr(tmpctx, der_keys + PUBKEY_DER_LEN, PUBKEY_DER_LEN));
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printf("# = 0x%s\n",
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tal_hexstr(tmpctx, &sha, sizeof(sha)));
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#endif
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*key = *basepoint;
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if (secp256k1_ec_pubkey_tweak_add(secp256k1_ctx,
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&key->pubkey, sha.u.u8) != 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# + basepoint (0x%s)\n",
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type_to_string(tmpctx, struct pubkey, basepoint));
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printf("# = 0x%s\n",
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type_to_string(tmpctx, struct pubkey, key));
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#endif
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return true;
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}
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/* BOLT #3:
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*
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* The corresponding private keys can be similarly derived, if the basepoint
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* secrets are known (i.e. the private keys corresponding to `localpubkey`,
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* `local_htlcpubkey`, and `local_delayedpubkey` only):
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*
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* privkey = basepoint_secret + SHA256(per_commitment_point || basepoint)
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*/
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bool derive_simple_privkey(const struct secret *base_secret,
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const struct pubkey *basepoint,
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const struct pubkey *per_commitment_point,
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struct privkey *key)
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{
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struct sha256 sha;
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unsigned char der_keys[PUBKEY_DER_LEN * 2];
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pubkey_to_der(der_keys, per_commitment_point);
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pubkey_to_der(der_keys + PUBKEY_DER_LEN, basepoint);
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sha256(&sha, der_keys, sizeof(der_keys));
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#ifdef SUPERVERBOSE
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printf("# SHA256(per_commitment_point || basepoint)\n");
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printf("# => SHA256(0x%s || 0x%s)\n",
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tal_hexstr(tmpctx, der_keys, PUBKEY_DER_LEN),
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tal_hexstr(tmpctx, der_keys + PUBKEY_DER_LEN, PUBKEY_DER_LEN));
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printf("# = 0x%s\n", tal_hexstr(tmpctx, &sha, sizeof(sha)));
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#endif
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key->secret = *base_secret;
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if (secp256k1_ec_privkey_tweak_add(secp256k1_ctx, key->secret.data,
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sha.u.u8) != 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# + basepoint_secret (0x%s)\n",
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tal_hexstr(tmpctx, base_secret, sizeof(*base_secret)));
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printf("# = 0x%s\n",
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tal_hexstr(tmpctx, key, sizeof(*key)));
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#endif
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return true;
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}
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/* BOLT #3:
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*
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* The `revocationpubkey` is a blinded key: when the local node wishes to
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* create a new commitment for the remote node, it uses its own
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* `revocation_basepoint` and the remote node's `per_commitment_point` to
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* derive a new `revocationpubkey` for the commitment. After the remote node
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* reveals the `per_commitment_secret` used (thereby revoking that
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* commitment), the local node can then derive the `revocationprivkey`, as it
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* now knows the two secrets necessary to derive the key
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* (`revocation_basepoint_secret` and `per_commitment_secret`).
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*
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* The `per_commitment_point` is generated using elliptic-curve multiplication:
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*
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* per_commitment_point = per_commitment_secret * G
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*
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* And this is used to derive the revocation pubkey from the remote node's
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* `revocation_basepoint`:
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*
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* revocationpubkey = revocation_basepoint * SHA256(revocation_basepoint || per_commitment_point) + per_commitment_point * SHA256(per_commitment_point || revocation_basepoint)
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*/
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bool derive_revocation_key(const struct pubkey *basepoint,
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const struct pubkey *per_commitment_point,
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struct pubkey *key)
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{
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struct sha256 sha;
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unsigned char der_keys[PUBKEY_DER_LEN * 2];
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secp256k1_pubkey add[2];
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const secp256k1_pubkey *args[2];
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pubkey_to_der(der_keys, basepoint);
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pubkey_to_der(der_keys + PUBKEY_DER_LEN, per_commitment_point);
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sha256(&sha, der_keys, sizeof(der_keys));
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#ifdef SUPERVERBOSE
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printf("# SHA256(revocation_basepoint || per_commitment_point)\n");
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printf("# => SHA256(0x%s || 0x%s)\n",
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tal_hexstr(tmpctx, der_keys, PUBKEY_DER_LEN),
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tal_hexstr(tmpctx, der_keys + PUBKEY_DER_LEN, PUBKEY_DER_LEN));
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printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
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#endif
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add[0] = basepoint->pubkey;
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if (secp256k1_ec_pubkey_tweak_mul(secp256k1_ctx, &add[0], sha.u.u8) != 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# x revocation_basepoint = 0x%s\n",
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type_to_string(tmpctx, secp256k1_pubkey, &add[0]));
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#endif
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pubkey_to_der(der_keys, per_commitment_point);
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pubkey_to_der(der_keys + PUBKEY_DER_LEN, basepoint);
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sha256(&sha, der_keys, sizeof(der_keys));
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#ifdef SUPERVERBOSE
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printf("# SHA256(per_commitment_point || revocation_basepoint)\n");
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printf("# => SHA256(0x%s || 0x%s)\n",
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tal_hexstr(tmpctx, der_keys, PUBKEY_DER_LEN),
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tal_hexstr(tmpctx, der_keys + PUBKEY_DER_LEN, PUBKEY_DER_LEN));
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printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
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#endif
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add[1] = per_commitment_point->pubkey;
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if (secp256k1_ec_pubkey_tweak_mul(secp256k1_ctx, &add[1], sha.u.u8) != 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# x per_commitment_point = 0x%s\n",
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type_to_string(tmpctx, secp256k1_pubkey, &add[1]));
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#endif
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args[0] = &add[0];
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args[1] = &add[1];
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if (secp256k1_ec_pubkey_combine(secp256k1_ctx, &key->pubkey, args, 2)
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!= 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# 0x%s + 0x%s => 0x%s\n",
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type_to_string(tmpctx, secp256k1_pubkey, args[0]),
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type_to_string(tmpctx, secp256k1_pubkey, args[1]),
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type_to_string(tmpctx, struct pubkey, key));
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#endif
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return true;
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}
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/* BOLT #3:
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*
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* The corresponding private key can be derived once the `per_commitment_secret`
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* is known:
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*
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* revocationprivkey = revocation_basepoint_secret * SHA256(revocation_basepoint || per_commitment_point) + per_commitment_secret * SHA256(per_commitment_point || revocation_basepoint)
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*/
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bool derive_revocation_privkey(const struct secret *base_secret,
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const struct secret *per_commitment_secret,
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const struct pubkey *basepoint,
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const struct pubkey *per_commitment_point,
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struct privkey *key)
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{
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struct sha256 sha;
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unsigned char der_keys[PUBKEY_DER_LEN * 2];
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struct secret part2;
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pubkey_to_der(der_keys, basepoint);
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pubkey_to_der(der_keys + PUBKEY_DER_LEN, per_commitment_point);
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sha256(&sha, der_keys, sizeof(der_keys));
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#ifdef SUPERVERBOSE
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printf("# SHA256(revocation_basepoint || per_commitment_point)\n");
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printf("# => SHA256(0x%s || 0x%s)\n",
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tal_hexstr(tmpctx, der_keys, PUBKEY_DER_LEN),
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tal_hexstr(tmpctx, der_keys + PUBKEY_DER_LEN, PUBKEY_DER_LEN));
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printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
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#endif
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key->secret = *base_secret;
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if (secp256k1_ec_privkey_tweak_mul(secp256k1_ctx, key->secret.data,
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sha.u.u8)
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!= 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# * revocation_basepoint_secret (0x%s)",
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tal_hexstr(tmpctx, base_secret, sizeof(*base_secret))),
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printf("# = 0x%s\n", tal_hexstr(tmpctx, key, sizeof(*key))),
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#endif
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pubkey_to_der(der_keys, per_commitment_point);
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pubkey_to_der(der_keys + PUBKEY_DER_LEN, basepoint);
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sha256(&sha, der_keys, sizeof(der_keys));
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#ifdef SUPERVERBOSE
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printf("# SHA256(per_commitment_point || revocation_basepoint)\n");
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printf("# => SHA256(0x%s || 0x%s)\n",
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tal_hexstr(tmpctx, der_keys, PUBKEY_DER_LEN),
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tal_hexstr(tmpctx, der_keys + PUBKEY_DER_LEN, PUBKEY_DER_LEN));
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printf("# = 0x%s\n", tal_hexstr(tmpctx, sha.u.u8, sizeof(sha.u.u8))),
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#endif
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part2 = *per_commitment_secret;
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if (secp256k1_ec_privkey_tweak_mul(secp256k1_ctx, part2.data,
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sha.u.u8) != 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# * per_commitment_secret (0x%s)",
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tal_hexstr(tmpctx, per_commitment_secret,
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sizeof(*per_commitment_secret))),
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printf("# = 0x%s\n", tal_hexstr(tmpctx, &part2, sizeof(part2)));
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#endif
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if (secp256k1_ec_privkey_tweak_add(secp256k1_ctx, key->secret.data,
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part2.data) != 1)
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return false;
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#ifdef SUPERVERBOSE
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printf("# => 0x%s\n", tal_hexstr(tmpctx, key, sizeof(*key)));
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#endif
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return true;
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}
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bool bip32_pubkey(const struct ext_key *bip32_base,
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struct pubkey *pubkey, u32 index)
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{
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const uint32_t flags = BIP32_FLAG_KEY_PUBLIC | BIP32_FLAG_SKIP_HASH;
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struct ext_key ext;
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if (index >= BIP32_INITIAL_HARDENED_CHILD)
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return false;
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if (bip32_key_from_parent(bip32_base, index, flags, &ext) != WALLY_OK)
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return false;
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if (!secp256k1_ec_pubkey_parse(secp256k1_ctx, &pubkey->pubkey,
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ext.pub_key, sizeof(ext.pub_key)))
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return false;
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return true;
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}
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