noa-receipt/dist/src/keys.js

NOA Agent Action Receipt — open, offline-verifiable provenance for AI-agent actions. The governance/receipt organ only; the NOA brain is separate and proprietary.

import { bufferFrom, bufToString, bufEquals, bufSubarray, byteLength, createPublicKeyCaptured, keyExportSpkiDer, keyExportPkcs8Der, createPrivateKeyCaptured, generateEd25519KeyPair, ed25519Sign, ed25519Verify, asymmetricKeyType, toBigInt, } from "./intrinsics.js";
import { membership } from "./inert.js";
const isSmallOrderPubkey = membership([
    "0100000000000000000000000000000000000000000000000000000000000000",
    "ecffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff7f",
    "0000000000000000000000000000000000000000000000000000000000000000",
    "0000000000000000000000000000000000000000000000000000000000000080",
    "26e8958fc2b227b045c3f489f2ef98f0d5dfac05d3c63339b13802886d53fc05",
    "26e8958fc2b227b045c3f489f2ef98f0d5dfac05d3c63339b13802886d53fc85",
    "c7176a703d4dd84fba3c0b760d10670f2a2053fa2c39ccc64ec7fd7792ac037a",
    "c7176a703d4dd84fba3c0b760d10670f2a2053fa2c39ccc64ec7fd7792ac03fa",
]);
export function generateKeyPair(kid) {
    const { publicKey, privateKey } = generateEd25519KeyPair();
    return {
        kid,
        publicKey: bufToString(keyExportSpkiDer(publicKey), "base64"),
        privateKey: bufToString(keyExportPkcs8Der(privateKey), "base64"),
    };
}
export function signEd25519(privateKeyB64, message) {
    const key = createPrivateKeyCaptured({
        key: bufferFrom(privateKeyB64, "base64"),
        format: "der",
        type: "pkcs8",
    });
    if (asymmetricKeyType(key) !== "ed25519")
        throw new Error("signEd25519: key is not an Ed25519 key");
    return bufToString(ed25519Sign(message, key), "base64");
}
export function verifyEd25519(publicKeyB64, message, signatureB64) {
    try {
        const der = bufferFrom(publicKeyB64, "base64");
        if (bufToString(der, "base64") !== publicKeyB64)
            return false;
        const key = createPublicKeyCaptured({ key: der, format: "der", type: "spki" });
        if (asymmetricKeyType(key) !== "ed25519")
            return false;
        const canonical = keyExportSpkiDer(key);
        if (!bufEquals(canonical, der))
            return false;
        const raw = bufSubarray(canonical, 12);
        const yBytes = bufferFrom(raw);
        yBytes[31] = yBytes[31] & 0x7f;
        const Q = (1n << 255n) - 19n;
        let y = 0n;
        for (let i = 31; i >= 0; i--)
            y = (y << 8n) | toBigInt(yBytes[i]);
        if (y >= Q)
            return false;
        if (isSmallOrderPubkey(bufToString(raw, "hex")))
            return false;
        const sigBytes = bufferFrom(signatureB64, "base64");
        if (byteLength(sigBytes) !== 64 || bufToString(sigBytes, "base64") !== signatureB64)
            return false;
        const L = 2n ** 252n + 27742317777372353535851937790883648493n;
        let S = 0n;
        for (let i = 63; i >= 32; i--)
            S = (S << 8n) | toBigInt(sigBytes[i]);
        if (S >= L)
            return false;
        return ed25519Verify(message, key, sigBytes);
    }
    catch {
        return false;
    }
}