/** Deterministic normalization: trim + lowercase. Deliberately minimal — over-normalizing
 * (e.g. stripping email +tags) would collapse distinct subjects into one. */
export declare function normalizeExternalId(id: string): string;
/** subject_hash = 'sh_' + base64url(HMAC-SHA256(pepper, normalize(external_id))). */
export declare function subjectHash(orgPepper: Uint8Array, externalId: string): Promise<string>;