Cryptographic protocol design in a two-party setting has often ignored the possibility of simultaneous message transmission by each of the two parties (i.e., using a duplex channel). In particular, most protocols for two-party key exchange have been designed assuming that parties alternate sending their messages (i.e., assuming a bidirectional half-duplex channel). However, by taking advantage of the communication characteristics of the network it may be possible to design protocols with improved latency. This is the focus of the present work. We present a number of provably-secure protocols for two-party authenticated key exchange (AKE) which require only a single round. Our first protocol provides key independence only, and is analyzed in the random oracle model. This scheme matches the most efficient AKE protocols among those found in the literature. Our second scheme additionally provides forward secrecy, and is also analyzed in the random oracle model. Our final protocol provides the same strong security guarantees, but is proven secure in the standard model. This scheme is only slightly less efficient (from a computational perspective) than the previous ones. These last two schemes are the first provably-secure one-round protocols for authenticated 2-party key exchange which provide forward secrecy.