Cryptanalysis of ring-LWE based key exchange with key share reuse, by Scott Fluhrer

This paper shows how several ring-LWE based key exchange protocols can be broken, under the assumption that the same key share is used for multiple exchanges. This indicates that, if these key exchange protocols are used, then it will be necessary for a fresh key share be generated for each exchange, and that these key exchange protocols cannot be used as a drop in replacement for designs which use Diffie-Hellman static key shares.