/**
 * Verify Meta webhook X-Hub-Signature-256 (HMAC-SHA256 over raw body).
 *
 * Meta computes signature over the *raw* request body, so callers must pass
 * the unparsed bytes (ArrayBuffer or Uint8Array) and the signature header.
 */
export declare function verifyMetaSignature(secret: string | null | undefined, rawBody: ArrayBuffer | Uint8Array, signatureHeader: string | null | undefined): Promise<boolean>;
export interface VerifyChallengeArgs {
    mode?: string | null;
    token?: string | null;
    challenge?: string | null;
    expectedToken: string | null;
}
export interface VerifyChallengeResult {
    ok: boolean;
    challenge?: string;
}
export declare function handleVerifyChallenge({ mode, token, challenge, expectedToken }: VerifyChallengeArgs): VerifyChallengeResult;
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