In this paper we describe ARM Microcontroller implementations of the Data Encryption Standard (DES) algorithm, with time-variable key technique to increase its immunity to Cryptanalysis attack. This proposed scheme changes the key with time. Using time-variable key technique enhances the security of DES because the same plain text is ciphered to different cipher texts by time. Hackers will face difficulty to hack into the proposed scheme because of time-variant behavior. This method provides more security against cryptanalysis attack than that provided by conventional old DES algorithm. LPC2148 ARM microcontroller was selected as the target for implementation with the embedded C as the software programming language.