ethers.js/src.ts/crypto/signing-key.ts

import * as secp256k1 from "@noble/secp256k1";

import {
    concat, dataLength, getBytes, getBytesCopy, hexlify, toHex,
    assertArgument
} from "../utils/index.js";

import { computeHmac } from "./hmac.js";
import { Signature } from "./signature.js";

import type { BytesLike } from "../utils/index.js";

import type { SignatureLike } from "./index.js";


//const N = BigInt("0xfffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141");

// Make noble-secp256k1 sync
secp256k1.utils.hmacSha256Sync = function(key: Uint8Array, ...messages: Array<Uint8Array>): Uint8Array {
    return getBytes(computeHmac("sha256", key, concat(messages)));
}

/**
 *  A **SigningKey** provides high-level access to the elliptic curve
 *  cryptography (ECC) operations and key management.
 */
export class SigningKey {
    #privateKey: string;

    /**
     *  Creates a new **SigningKey** for %%privateKey%%.
     */
    constructor(privateKey: BytesLike) {
        assertArgument(dataLength(privateKey) === 32, "invalid private key", "privateKey", "[REDACTED]");
        this.#privateKey = hexlify(privateKey);
    }

    /**
     *  The private key.
     */
    get privateKey(): string { return this.#privateKey; }

    /**
     *  The uncompressed public key.
     *
     * This will always begin with the prefix ``0x04`` and be 132
     * characters long (the ``0x`` prefix and 130 hexadecimal nibbles).
     */
    get publicKey(): string { return SigningKey.computePublicKey(this.#privateKey); }

    /**
     *  The compressed public key.
     *
     *  This will always begin with either the prefix ``0x02`` or ``0x03``
     *  and be 68 characters long (the ``0x`` prefix and 33 hexadecimal
     *  nibbles)
     */
    get compressedPublicKey(): string { return SigningKey.computePublicKey(this.#privateKey, true); }

    /**
     *  Return the signature of the signed %%digest%%.
     */
    sign(digest: BytesLike): Signature {
        assertArgument(dataLength(digest) === 32, "invalid digest length", "digest", digest);

        const [ sigDer, recid ] = secp256k1.signSync(getBytesCopy(digest), getBytesCopy(this.#privateKey), {
            recovered: true,
            canonical: true
        });

        const sig = secp256k1.Signature.fromHex(sigDer);
        return Signature.from({
            r: toHex("0x" + sig.r.toString(16), 32),
            s: toHex("0x" + sig.s.toString(16), 32),
            v: (recid ? 0x1c: 0x1b)
        });
    }

    /**
     *  Returns the [[link-wiki-ecdh]] shared secret between this
     *  private key and the %%other%% key.
     *
     *  The %%other%% key may be any type of key, a raw public key,
     *  a compressed/uncompressed pubic key or aprivate key.
     *
     *  Best practice is usually to use a cryptographic hash on the
     *  returned value before using it as a symetric secret.
     */
    computeShardSecret(other: BytesLike): string {
        const pubKey = SigningKey.computePublicKey(other);
        return hexlify(secp256k1.getSharedSecret(getBytesCopy(this.#privateKey), pubKey));
    }

    /**
     *  Compute the public key for %%key%%, optionally %%compressed%%.
     *
     *  The %%key%% may be any type of key, a raw public key, a
     *  compressed/uncompressed public key or private key.
     */
    static computePublicKey(key: BytesLike, compressed?: boolean): string {
        let bytes = getBytes(key, "key");

        if (bytes.length === 32) {
            const pubKey = secp256k1.getPublicKey(bytes, !!compressed);
            return hexlify(pubKey);
        }

        if (bytes.length === 64) {
            const pub = new Uint8Array(65);
            pub[0] = 0x04;
            pub.set(bytes, 1);
            bytes = pub;
        }

        const point = secp256k1.Point.fromHex(bytes);
        return hexlify(point.toRawBytes(compressed));
    }

    /**
     *  Returns the public key for the private key which produced the
     *  %%signature%% for the given %%digest%%.
     */
    static recoverPublicKey(digest: BytesLike, signature: SignatureLike): string {
        assertArgument(dataLength(digest) === 32, "invalid digest length", "digest", digest);

        const sig = Signature.from(signature);
        const der = secp256k1.Signature.fromCompact(getBytesCopy(concat([ sig.r, sig.s ]))).toDERRawBytes();

        const pubKey = secp256k1.recoverPublicKey(getBytesCopy(digest), der, sig.yParity);
        if (pubKey != null) { return hexlify(pubKey); }

        assertArgument(false, "invalid signautre for digest", "signature", signature);
    }

    /**
     *  Returns the point resulting from adding the ellipic curve points
     *  %%p0%% and %%p1%%.
     *
     *  This is not a common function most developers should require, but
     *  can be useful for certain privacy-specific techniques.
     *
     *  For example, it is used by [[HDNodeWallet]] to compute child
     *  addresses from parent public keys and chain codes.
     */
    static addPoints(p0: BytesLike, p1: BytesLike, compressed?: boolean): string {
        const pub0 = secp256k1.Point.fromHex(SigningKey.computePublicKey(p0).substring(2));
        const pub1 = secp256k1.Point.fromHex(SigningKey.computePublicKey(p1).substring(2));
        return "0x" + pub0.add(pub1).toHex(!!compressed)
    }
}

/*
const key = new SigningKey("0x1234567890123456789012345678901234567890123456789012345678901234");
console.log(key);
console.log(key.sign("0x1234567890123456789012345678901234567890123456789012345678901234"));
{
  const privKey = "0x1234567812345678123456781234567812345678123456781234567812345678";
  const signingKey = new SigningKey(privKey);
  console.log("0", signingKey, signingKey.publicKey, signingKey.publicKeyCompressed);

  let pubKey = SigningKey.computePublicKey(privKey);
  let pubKeyComp = SigningKey.computePublicKey(privKey, true);
  let pubKeyRaw = "0x" + SigningKey.computePublicKey(privKey).substring(4);
  console.log("A", pubKey, pubKeyComp);

  let a = SigningKey.computePublicKey(pubKey);
  let b = SigningKey.computePublicKey(pubKey, true);
  console.log("B", a, b);

  a = SigningKey.computePublicKey(pubKeyComp);
  b = SigningKey.computePublicKey(pubKeyComp, true);
  console.log("C", a, b);

  a = SigningKey.computePublicKey(pubKeyRaw);
  b = SigningKey.computePublicKey(pubKeyRaw, true);
  console.log("D", a, b);

  const digest = "0x1122334411223344112233441122334411223344112233441122334411223344";
  const sig = signingKey.sign(digest);
  console.log("SS", sig, sig.r, sig.s, sig.yParity);

  console.log("R", SigningKey.recoverPublicKey(digest, sig));
}
*/