export interface DownloadProgress {
    percent: number;
    transferred: number;
    total: number;
}
/**
 * Downloader handles secure asset downloads, SHA256, and GPG validation.
 * Used internally by Updater.
 */
export declare class Downloader {
    /**
     * Downloads an asset to the given path, with optional progress and SHA256 validation.
     * @param assetUrl URL to download
     * @param destPath Local file path to save
     * @param onProgress Optional progress callback
     * @param expectedSha256 Optional SHA256 hash to validate
     * @returns Path to downloaded file
     * @throws Error if download or hash validation fails
     */
    downloadAsset(assetUrl: string, destPath: string, onProgress?: (progress: DownloadProgress) => void, expectedSha256?: string): Promise<string>;
    /**
     * Validates a file's SHA256 hash.
     * @param filePath Path to file
     * @param expected Expected SHA256 hash
     * @throws Error if hash does not match
     */
    validateSha256(filePath: string, expected: string): Promise<void>;
    /**
     * Validates a file's GPG signature using a detached .sig file.
     * @param filePath Path to file
     * @param sigPath Path to .sig file
     * @param keyringPath Optional keyring
     * @throws Error if signature is invalid
     */
    validateGpg(filePath: string, sigPath: string, keyringPath?: string): Promise<void>;
}