In this paper, we study the two transmitter multiple-access channel with noncausal side information (NSI) at one (single-sided) or both (two-sided) of the encoders in the presence of an external wiretapper and under individual and collective secrecy constraints. Our work consists of four parts. (i) First, we consider the discrete memoryless (DM-MAC-WT) case of the model and derive inner and outer bounds on the secrecy capacity region under both of the secrecy constraints. (ii)Next, the results are extended to the Gaussian memoryless case (GMAC-WT) in detail and are used to illustrate numerically that the secrecy rate region is enlarged by increasing the power of the interference signal which is known non-causally at the encoder. (iii) Then, we analyse the strong interference regime as an important regime in Gaussian multiple-access channels with side information and show that under collective secrecy constraint, we can achieve the secrecy capacity region of the single-sided channel asymptotically for a special case in which the signal and noise powers satisfy specific constraints. To the best of our knowledge, this capacity region is the first one obtained for GMAC-WT. (iv) Moreover, we show that our results include previous works as its special cases for both the singlesided and two-sided channel models.

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