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<span>The data encryption is one of the most critical issues in the communication system design. Nowadays, many encryption algorithms are being updated to keep pace with the remarkable progress in the communication field. The advanced encryption standard (AES) is a common algorithm that has proved its efficacy. The main drawback of AES is that it uses too simple algebraic structures, since every block is always encrypted in the same way that makes the hacking process possible if the hacker captures the key and the uses S-Box in the input stage. This especially applies to the unwired communication systems where chances of hacking exceed those found in the wired systems. The paper proposes a security enhancement method that is based on utilizing concatenated AES and international data encryption algorithm (IDEA) algorithms. Upon applying the proposed algorithm, the hacking process becomes a great challenge. The paper incorporates the real-time FPGA implementation of the proposed algorithm in the encryption and the decryption stages. Besides, the paper presents a clear analysis of the system’s performance.</span>

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Abstract. Time interval (TI) is one of the basic quantities. Its measurement is not included only in the activities running in the time and frequency metrology but also included in the measurement of many other quantities that depend on time interval measurement (TIM). This means that improving the accuracy and reducing the measurement uncertainty of TI will reflect also on improving the accuracy and reducing the measurement uncertainty of many other quantities. To do that, we need to decrease or eliminate the effect of the dominant factors that degrade the quality of TIM. One of the major contributors to the measurement uncertainty of TI is the internal error of the time interval counter (TIC) used in the measurement. In this paper we introduce a methodology with which we can estimate precisely the internal error of the counter and eliminate its effect.