NIP-17 exposes the recipient's identity and lacks both forward and backward secrecy. However, its advantage lies in better multi-device synchronization capabilities. Because the encryption key and receiving address remain unchanged, users can receive and decrypt all messages simply by importing their nsec. NIP-17 is designed for DM in microblogging applications, not as a standalone chat application. It prioritizes multi-device synchronization over enhanced encryption security. This is not a flaw, as it has suitable application scenarios.