  In this paper, we introduce two new achievable schemes for the fading
multiple access wiretap channel (MAC-WT). In the model that we consider, we
assume that perfect knowledge of the state of all channels is available at all
the nodes in a causal fashion. Our schemes use this knowledge together with the
time varying nature of the channel model to align the interference from
different users at the eavesdropper perfectly in a one-dimensional space while
creating a higher dimensionality space for the interfering signals at the
legitimate receiver hence allowing for better chance of recovery. While we
achieve this alignment through signal scaling at the transmitters in our first
scheme (scaling based alignment (SBA)), we let nature provide this alignment
through the ergodicity of the channel coefficients in the second scheme
(ergodic secret alignment (ESA)). For each scheme, we obtain the resulting
achievable secrecy rate region. We show that the secrecy rates achieved by both
schemes scale with SNR as 1/2log(SNR). Hence, we show the sub-optimality of the
i.i.d. Gaussian signaling based schemes with and without cooperative jamming by
showing that the secrecy rates achieved using i.i.d. Gaussian signaling with
cooperative jamming do not scale with SNR. In addition, we introduce an
improved version of our ESA scheme where we incorporate cooperative jamming to
achieve higher secrecy rates. Moreover, we derive the necessary optimality
conditions for the power control policy that maximizes the secrecy sum rate
achievable by our ESA scheme when used solely and with cooperative jamming.
