/**
 * Service for encrypting and decrypting message content.
 *
 * @remarks
 * Uses ECIES for direct message encryption with recipient public keys.
 * Uses AES-256-GCM with shared key for broadcast messages.
 *
 * @see Requirements 3.1, 3.2, 3.3, 3.5
 */
export declare class MessageEncryptionService {
    /**
     * Encrypt content for direct message with recipient public keys.
     * @param content - Plaintext content
     * @param recipientPublicKeys - Map of recipient ID to public key
     * @returns Encrypted content and per-recipient encrypted keys
     */
    encryptDirect(content: Uint8Array, recipientPublicKeys: Map<string, Uint8Array>): Promise<{
        encryptedContent: Uint8Array;
        encryptedKeys: Map<string, Uint8Array>;
    }>;
    /**
     * Encrypt content for broadcast with shared key.
     * @param content - Plaintext content
     * @param sharedPublicKey - Shared public key for broadcast
     * @returns Encrypted content
     */
    encryptBroadcast(content: Uint8Array, sharedPublicKey: Uint8Array): Promise<Uint8Array>;
    /**
     * Decrypt message content (no automatic decryption in storage/routing).
     * @param encryptedContent - Encrypted content
     * @param privateKey - Private key for decryption
     * @returns Decrypted content
     */
    decrypt(encryptedContent: Uint8Array, privateKey: Uint8Array): Promise<Uint8Array>;
    /**
     * Decrypt symmetric key for recipient.
     * @param encryptedKey - Encrypted symmetric key
     * @param privateKey - Recipient's private key
     * @returns Decrypted symmetric key
     */
    decryptKey(encryptedKey: Uint8Array, privateKey: Uint8Array): Promise<Uint8Array>;
}
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