/**
 * WeChat 媒体加解密
 *
 * AES-128-ECB 加密，用于 CDN 上传/下载
 */
import type { WeixinCredentials, MessageItem } from './weixin-types.js';
/**
 * 生成随机 16 字节 AES 密钥
 */
export declare function generateMediaKey(): Buffer;
/**
 * AES-128-ECB 加密（PKCS7 填充）
 */
export declare function encryptMedia(data: Buffer, key: Buffer): Buffer;
/**
 * AES-128-ECB 解密（PKCS7 去填充）
 */
export declare function decryptMedia(data: Buffer, key: Buffer): Buffer;
/**
 * 计算填充后密文大小
 */
export declare function aesEcbPaddedSize(plaintextSize: number): number;
/**
 * 从 CDN 下载并解密媒体
 */
export declare function downloadAndDecryptMedia(cdnUrl: string, aesKey: Buffer, label?: string): Promise<Buffer>;
/**
 * 从消息项下载媒体
 */
export declare function downloadMediaFromItem(item: MessageItem, cdnBaseUrl: string): Promise<{
    data: Buffer;
    mimeType: string;
    filename: string;
} | null>;
/**
 * 加密并上传媒体到 CDN
 */
export declare function uploadMediaToCdn(creds: WeixinCredentials, data: Buffer, filename: string, mediaType: number): Promise<{
    encryptQueryParam: string;
    aesKeyBase64: string;
    cipherSize: number;
}>;
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