Abstract: In order to resist attacks of quantum computing and protect the privacy and data security of underwater nodes, a multi-party key encapsulation mechanism based on the Internet of underwater things is proposed using the difficulty assumption of NTRU cryptographic system.Firstly, the pseudo-identities of device serial numbers are generated by combining ocean sensor acoustic sequences and underwater acoustic waveform factorization, and a verifiable identity ocean acoustic message code is designed.Secondly, a key generation algorithm suitable for underwater communication is designed using orthogonal frequency division multiplexing (OFDM) frequency domain oversampling technique and number theoretic transform (NTT).On this basis, a multi-party public key encryption algorithm with indistinguishability and anonymity under chosen plaintext attack (IND-Anon-CPA) security is constructed using identity-bound hybrid encryption and ocean noise-based obfuscation operation, Thirdly, a SeaFO transform based on ocean noise is introduced to develop a multi-party key encapsulation algorithm with indistinguishability and anonymity under chosen ciphertext attack (IND-Anon-CCA) security without full re-encryption process.Finally, a novel session key update mechanism is devised where autonomous underwater vehicles verify ciphertext components and assess pseudo-identity and timestamp validity using OFDM subcarriers. The new session keys are decapsulated using SeaFO transform, which not only achieve implicit rejection in multi-party environments and but also thwart adversaries’ adaptive corruption on SeaNTRU.Security analysis demonstrates that SeaNTRU has the characteristics of resistance to key replacement attack, replay attack, and man-in-the-middle attack.Experimental results show that SeaNTRU has lower computational cost and communication overhead than the existing schemes.