ANSI X9.42 [ANS94a] is a draft standard for key agreement based on the Diffie-Hellman algorithm, and ANSI X9.44 [ANS94b] is a draft standard for key transport based on the RSA algorithm. The former is intended to specify techniques for deriving a shared secret key; techniques currently being considered include basic Diffie-Hellman (see Question 24), authenticated Diffie-Hellman (see Question 25), and the MQV protocols [MQV95]. Some work to unify the various approaches is currently in progress. ANSI X9.44 will specify techniques for transporting a secret key with the RSA algorithm. It is currently based on IBM's Optimal Asymmetric Encryption Padding, a "provably secure" padding technique related to work by Bellare and Rogaway [BR94].
ANSI X9.42 was previously part of ANSI X9.30, and ANSI X9.44 was previously part of ANSI X9.31 (See Question 160).