@node-dlc/core/dist/lightning/CommitmentSecret.js

DLC Core

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
exports.CommitmentSecret = void 0;
const crypto_1 = require("@node-dlc/crypto");
class CommitmentSecret {
    /**
     * Generic version of commitment secret generator as defined in
     * BOLT3.
     *
     * This function works by decrementing from bits to 0. If the index
     * number has the corresponding bit set, it flips the bit in the
     * secret and hashes it.
     *
     * The natural conclusion is the first secret flips every bit and
     * the last secret flips zero (and is thus the seed).
     *
     * This function can be used for generate the local per-commitment
     * secret based on the per-commitment seed and a commitment index
     * (in this case it) generates all 48 bits.
     *
     * This function can also be used to generate prior commitment
     * secrets from a newer secret, which acts as a prefix.
     *
     * @param base base secret that will be used to derive from
     * @param i secret at index I to generate
     * @param bits bits to evaluate, default is 48
     */
    static derive(base, i, bits = 48) {
        // intii
        let p = Buffer.from(base);
        for (let b = bits - 1; b >= 0; b--) {
            if (i & (BigInt(1) << BigInt(b))) {
                // flip the specified bit in the specific byte
                const byteIndex = Math.floor(b / 8);
                const bitIndex = b % 8;
                p[byteIndex] = p[byteIndex] ^ (1 << bitIndex);
                p = (0, crypto_1.sha256)(p);
            }
        }
        return p;
    }
}
exports.CommitmentSecret = CommitmentSecret;
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