/**
 * Interface for recipient public key provider.
 * Implementations can fetch keys from node registry, discovery protocol, etc.
 */
export interface IPublicKeyProvider {
    getPublicKey(nodeId: string): Promise<Uint8Array | null>;
}
/**
 * Manager for recipient public key operations.
 *
 * @remarks
 * Fetches and validates recipient public keys for message encryption.
 * Handles missing keys gracefully.
 *
 * @see Requirements 3.1
 */
export declare class RecipientKeyManager {
    private keyProvider;
    constructor(keyProvider: IPublicKeyProvider);
    /**
     * Fetch public keys for multiple recipients.
     * @param recipientIds - Array of recipient node IDs
     * @returns Map of recipient ID to public key
     * @throws MessageError if any required key is missing
     */
    fetchPublicKeys(recipientIds: string[]): Promise<Map<string, Uint8Array>>;
    /**
     * Validate public key format and length.
     * @param publicKey - Public key to validate
     * @returns True if valid secp256k1 public key
     */
    validatePublicKey(publicKey: Uint8Array): boolean;
    /**
     * Fetch public key for single recipient with graceful handling.
     * @param recipientId - Recipient node ID
     * @returns Public key or null if not found
     */
    fetchPublicKeyOptional(recipientId: string): Promise<Uint8Array | null>;
}
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