Recently, the increase in the use of fast and reliable communication systems has increased the significance and utilization of satellite-based communication systems. The communication systems used in the space environment is more reliable and robust as compared to communication systems used on earth. Because unlike ground communication, the communication systems in space have to bear harsh space environment and its effects like radiations, pressure, and vacuum, which causes anomalies in

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... ation systems. These effects are known as Single Event Effects (SEE), which results in loss of data or sometimes even damage to the equipment. Like ground systems, in satellite, the Advanced Encryption Standard (AES) is a widely used encryption algorithm which is not only used to provide data confidentiality but also used in data authentication & integrity algorithms (e.g. CMAC) as well as in authenticated encryption (AE) algorithm (e.g., AES-GCM). The Substitution Box (S-Box) is a main component of the AES algorithm, which is generally implemented on memory blocks. The memory blocks in space are vulnerable to radiations and mostly affected by SEE; hence, protection techniques against SEE are proposed by researchers. Two methods for implementation of the S-Box algorithm are by a look-up table or by an algorithm. In this work, analysis of using these two methods of the S-Box implementation for SEE is performed. The implementation of both methods is performed on FPGA, and results show that the algorithm implementation is more reliable in the space environment as compared to table-based implementation. the development of more sophisticated systems on earth. The data security in communication systems used in space are more critical as the only source of contact between spacecraft and humans on earth is through communication systems. The effects causing an unreliable response of communication systems are under constant development. It has stimulated a trend that challenges researchers to develop equipment and communication systems for the space environment. In the space environment, the significant effects on communication systems are space radiations. The radiations cause unreliable operation of communication systems. The space radiations cause's effects called the Single Event Effects (SEE); these effects cause the electronics in communication systems to malfunction. The primary source of space radiations is incident cosmic rays and incident high energy protons (mostly origin from solar flares or Van Allen radiation belt around the earth). There are three main types of SEE. The effect of radiations causing a bit to flip is known as Single Event Upset (SEU). The latch-up of memory caused by a high operating current is known as Single Event Latch-up (SEL). The radiations effects causing burn-out of memory is called Single Event Burn-out (SEB). These effects can cause permanent and temporary damages depend on the type of effect on memory. Therefore, in communication systems, the system must be capable of tolerating SEE. The SEE is more effective on memories such as Static Random Access Memory (SRAM). These SEE are not new, and many researchers have diagnosed these effects in the space environment [1], [2] . These effects are more effective in memories, and many researchers worked on the methods to avoid these effects on hardware and software [3]- [5] . The implementation methods for avoiding the SEE are usually focus on the SEU, and these effects consume a large area to implement as compared to the area of the original design. The implementation of Triple Memory Redundancy (TMR) requires triplication of memory resources. In the scope of security of communication systems for space communication the Consultative Committee for Space Data Systems (CCSDS) recommends the use of Advanced Encryption Standard (AES) algorithm [6] . Although with the increasing trend of high-speed communication the AES in Counter mode (AES-CTR) [7] is utilized widely in much high-speed Authenticated Encryption (AE) algorithms such as Galois Counter Mode (GCM) [8] . In the AES algorithm, amongst the four sub-operations, the Substitution byte (S-byte) operation involves the substitution of byte from Substitution Box (S-Box) consumes memory for implementation. The S-Box can be implemented using the look-up table implementation or algorithm-based implementation. The look-up table implementation or the table-based implementation is usually stored in memory, such as SRAM. However, in the space environment, the memory on exposure to radiations may cause the SEE. On the other hand, in algorithm-based implementation implements the algorithm using logic gates instead of memory. The algorithm-based implementation avoids the memory resources and implements the on logic gates make the implementation less affected by SEE.