We propose a new post-quantum key exchange algorithm based on the integer module learning with errors (I-MLWE) problem. Our ThreeBears algorithm is simple and performant. Our main goal is to explore a wider space of LWE designs: integer rings instead of polynomial rings; Melas forward error correction; compressed private keys; and a new Fujisaki-Okamoto variant to protect against chosen-ciphertext attacks.
The NIST round 2 specification includes small parameter changes to reduce the failure probability. It also includes an implicit rejection mode, which is optional pending further research into CCA transforms.