AES Encryption on voice

Is it possible to have audio sample from A0 and encrypt it using AES-128 and decrypt it on another Arduino

Yes, for a small sample, and rather slowly on a standard Arduino.

You might want to look at the Ti MSP432 Launchpad. It has built in hardware AES acceleration and can perform a 128 bit encryption in 168 clock cycles, or 3.5 us at 48MHz.