BOLT #3: * * The corresponding private keys can be similarly derived, if the basepoint * secrets are known (i.e. the private keys corresponding to `localpubkey`, * `local_htlcpubkey`, and `local_delayedpubkey` only): * * privkey = basepoint_secret + SHA256(per_commitment_point || basepoint) */
| 71 | * privkey = basepoint_secret + SHA256(per_commitment_point || basepoint) |
| 72 | */ |
| 73 | bool derive_simple_privkey(const struct secret *base_secret, |
| 74 | const struct pubkey *basepoint, |
| 75 | const struct pubkey *per_commitment_point, |
| 76 | struct privkey *key) |
| 77 | { |
| 78 | struct sha256 sha; |
| 79 | unsigned char der_keys[PUBKEY_CMPR_LEN * 2]; |
| 80 | |
| 81 | pubkey_to_der(der_keys, per_commitment_point); |
| 82 | pubkey_to_der(der_keys + PUBKEY_CMPR_LEN, basepoint); |
| 83 | sha256(&sha, der_keys, sizeof(der_keys)); |
| 84 | #ifdef SUPERVERBOSE |
| 85 | printf("# SHA256(per_commitment_point || basepoint)\n"); |
| 86 | printf("# => SHA256(0x%s || 0x%s)\n", |
| 87 | tal_hexstr(tmpctx, der_keys, PUBKEY_CMPR_LEN), |
| 88 | tal_hexstr(tmpctx, der_keys + PUBKEY_CMPR_LEN, PUBKEY_CMPR_LEN)); |
| 89 | printf("# = 0x%s\n", tal_hexstr(tmpctx, &sha, sizeof(sha))); |
| 90 | #endif |
| 91 | |
| 92 | key->secret = *base_secret; |
| 93 | if (secp256k1_ec_seckey_tweak_add(secp256k1_ctx, key->secret.data, |
| 94 | sha.u.u8) != 1) |
| 95 | return false; |
| 96 | #ifdef SUPERVERBOSE |
| 97 | printf("# + basepoint_secret (0x%s)\n", |
| 98 | tal_hexstr(tmpctx, base_secret, sizeof(*base_secret))); |
| 99 | printf("# = 0x%s\n", |
| 100 | tal_hexstr(tmpctx, key, sizeof(*key))); |
| 101 | #endif |
| 102 | return true; |
| 103 | } |
| 104 | |
| 105 | /* BOLT #3: |
| 106 | * |