export declare class Ed25519KeypairService {
    private cached;
    isSupported(): boolean;
    /** Returns the device's Ed25519 keypair, generating and persisting one on first use. */
    getOrCreateKeyPair(): Promise<{
        publicKeyBase64: string;
    }>;
    sign(message: string): Promise<string>;
    /** Discards the local keypair (e.g. "forget this device"). A new keypair on next login requires re-registration with the backend. */
    clear(): Promise<void>;
    private generateAndPersist;
    private loadFromStore;
    private openDatabase;
    private toBase64;
}