@hpke/dhkem-x25519/esm/src/hkdfSha256.js

A Hybrid Public Key Encryption (HPKE) module extension for X25519

import { hmac } from "@noble/hashes/hmac";
import { sha256 } from "@noble/hashes/sha256";
import { HkdfSha256Native } from "@hpke/common";
export class HkdfSha256 extends HkdfSha256Native {
    async extract(salt, ikm) {
        await this._setup();
        if (salt.byteLength === 0) {
            salt = new ArrayBuffer(this.hashSize);
        }
        if (salt.byteLength !== this.hashSize) {
            return hmac(sha256, new Uint8Array(salt), new Uint8Array(ikm))
                .buffer;
        }
        const key = await this._api.importKey("raw", salt, this.algHash, false, [
            "sign",
        ]);
        return await this._api.sign("HMAC", key, ikm);
    }
}