Public key exchange with authenicated ECDHE and security against quantum computers

A device to securely communicate with a network using elliptic curve cryptography and post-quantum cryptography, the device comprising:

• a nonvolatile memory to store (i) first cryptographic parameters for conducting an elliptic curve Diffie Hellman (ECDH) key exchange, (ii) second cryptographic parameters for conducting a post-quantum cryptography key encapsulation mechanism (PQC-KEM);
• a network interface communicating with a wide-area network to:
• a) transmit, to the network, a first message comprising (i) a first device ephemeral public key supporting the first cryptographic parameters, and (i) a second device ephemeral public key supporting the second cryptographic parameters,
• b) receive, from the network, a second message comprising a server ephemeral public key and a first symmetric ciphertext, wherein a first plaintext within the first symmetric ciphertext comprises a ciphertext for the PQC-KEM, and
• c) transmit, to the network, a third message comprising a second symmetric ciphertext;
• a random access memory to store computer executable instructions for the device to generate:
• a) a first device ephemeral private key for the first device ephemeral public key and the first cryptographic parameters,
• b) a second device ephemeral private key for the second device ephemeral public key and the second cryptographic parameters,
• c) a first shared secret from the ECDH key exchange with the first device ephemeral private key and the server ephemeral public key,
• d) a first symmetric ciphering key from a first key derivation function (KDF) with at least the first shared secret,
• e) a second shared secret output from the PQC-KEM with (i) the ciphertext for the PQC-KEM and (ii) the second device ephemeral private key, and
• f) a second symmetric ciphering key from a second KDF with at least the second shared secret;
• a processor to:
• a) decrypt the first symmetric ciphertext with the first symmetric ciphering key in order to read the first plaintext comprising the ciphertext for the PQC-KEM, and
• b) generate the second symmetric ciphertext by encrypting a second plaintext with the second symmetric ciphering key, the second plaintext comprising device data.