/**
 * Decode an AES key from CDNMedia.aes_key (base64-encoded).
 * Two formats exist:
 *   A: base64(raw 16 bytes) → decoded length = 16 → use directly
 *   B: base64(hex string 32 ASCII chars) → decoded length = 32 → hex-decode to 16 bytes
 */
export declare function decodeAesKey(aesKeyBase64: string): Buffer;
/**
 * Decode an AES key from image_item.aeskey (raw 32-char hex string).
 */
export declare function decodeHexAesKey(hexKey: string): Buffer;
/**
 * Encrypt plaintext with AES-128-ECB + PKCS7 padding.
 */
export declare function encryptAesEcb(plaintext: Buffer, key: Buffer): Buffer;
/**
 * Decrypt AES-128-ECB + PKCS7 ciphertext.
 */
export declare function decryptAesEcb(ciphertext: Buffer, key: Buffer): Buffer;
/**
 * Calculate AES-128-ECB ciphertext size (with PKCS7 padding).
 * Formula: ceil((rawsize + 1) / 16) * 16
 */
export declare function calcEncryptedSize(rawSize: number): number;
/**
 * Generate a random 16-byte AES key as hex string (for uploads).
 */
export declare function randomAesKeyHex(): string;
/**
 * Generate X-WECHAT-UIN header value:
 * random uint32 → decimal string → base64
 */
export declare function randomWechatUin(): string;
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