Secure session resumption using post-quantum cryptography

A method for a device to conduct secure communications with a network, the method performed by the device, the method comprising:

• a) storing, in nonvolatile memory, a plurality of key encapsulation mechanism (KEM) algorithms comprising a first KEM algorithm;
• b) generating, by a processing unit, a device ephemeral private key and a corresponding device ephemeral public key for the first KEM algorithm;
• c) transmitting, to the network via a network interface, a first message comprising (i) the device ephemeral public key, and (ii) identifiers for each of the plurality of KEM algorithms and the first KEM algorithm;
• d) receiving, from the network via the network interface, a second message comprising a first asymmetric ciphertext and a first symmetric ciphertext of at least a server public key for a second KEM algorithm;
• e) conducting a KEM decapsulation (DECAPS) function to generate a first shared secret K1 using the first asymmetric ciphertext and the first KEM algorithm;
• f) conducting a KEM encapsulation (ENCAPS) function to generate a second shared secret K2 and a second asymmetric ciphertext using at least (i) the server public key and (ii) the second KEM algorithm;
• g) deriving a symmetric ciphering key S2 using at least the K1 and the K2;
• h) deriving a “pre-shared” secret key (PSK) using at least the K1 and the K2;
• i) receiving, from the network, a third message comprising a second symmetric ciphertext of an identity of the PSK (PSK-ID), wherein the device decrypts the second symmetric ciphertext with the key S2;
• j) transmitting, to the network, a fourth message requesting resumption of a secure session, the fourth message comprising the PSK-ID and a random number generated by the device;
• k) generating a symmetric ciphering key S3 using the PSK and the random number;
• l) Receiving, from the network, a third symmetric ciphertext;
• and
• m) decrypting the third symmetric ciphertext using the key S3.