/**
 * Cross-platform key storage abstraction.
 *
 * Provides a unified interface for storing the Aegis master key in
 * OS-managed credential stores, keeping it out of plaintext files.
 *
 * Resolution order (auto-detect):
 *   macOS   → Keychain (`security` CLI)
 *   Windows → Credential Manager (`cmdkey` + PowerShell)
 *   Linux   → Secret Service (`secret-tool` / libsecret)
 *   Fallback → File (.aegis/.master-key, mode 0600)
 */
/** Backend identifier for display and diagnostics. */
export type KeyStorageBackend = 'macos-keychain' | 'windows-credential-manager' | 'linux-secret-service' | 'file';
/** Abstract key storage interface. All methods are synchronous to keep config loading simple. */
export interface KeyStorage {
    /** Human-readable backend name (e.g. "macOS Keychain"). */
    readonly name: string;
    /** Machine-readable backend identifier. */
    readonly backend: KeyStorageBackend;
    /** Check whether this backend is available on the current system. */
    isAvailable(): boolean;
    /** Retrieve the master key. Returns undefined if not stored. */
    getKey(): string | undefined;
    /** Store the master key (creates or replaces). */
    setKey(key: string): void;
    /** Delete the stored master key. No-op if not present. */
    deleteKey(): void;
}
/** Check whether a CLI tool exists on PATH. Results are cached per process. */
export declare function commandExists(command: string): boolean;
/** Clear the commandExists cache (for testing). */
export declare function clearCommandExistsCache(): void;
/**
 * Auto-detect the best available key storage backend for the current platform.
 *
 * @param dataDir  Path to the .aegis data directory (used by file fallback).
 * @returns        A KeyStorage implementation.
 */
export declare function getKeyStorage(dataDir: string): KeyStorage;
//# sourceMappingURL=key-storage.d.ts.map