Noise is unwanted electrical or electromagnetic radiation that degrades the quality of the signal and the data. It can be difficult to denoise a signal that has been acquired in a noisy environment, but doing so may be necessary in a number of signal processing applications. This paper extends the issue of signal denoising from signals with regular structures, which are affected by noise, to signals with irregular structures by applying the graph signal processing (GSP) technique and a very wellknown filter, the standard Kalman filter, after adjusting it. When the modified Kalman filter is compared to the standard Kalman filter, the modified one performs better in situations where there are uncertain observations and/or processing noise and shows the best results. Also, the modified Kalman filter showed a higher efficiency when we compared it with other filters for different types of noise, which are not only standard Gaussian noises but also uniform distribution noise across two intervals for uncertain observation noise.

RC4 stream cipher is one of the most significant symmetric cryptosystems, it is simple and used in many commercial products. RC4 uses dynamic permutations and avoids using Linear Feed Back Shift Register (LFSR). It has many weaknesses, such as the tendency in the generated key stream that some key bytes are biased toward different values. This paper presents a new algorithm using S-box of Advanced Encryption Standard (AES) to solve the correlation between public known outputs of the internal state. The state table is filled from S-box values and additional swapping operations are used. The analysis of the proposed algorithm over variable key length produces key byte streams that have no single and double bias. This paper obtains a new algorithm that combines the efficiency of the RC4 and robustness of AES. The results show that the sequences that are generated by the developed RC4 are more random than the sequence that was generated by the RC4. Also, the developed algorithm demands little time more than RC4 execution time. Additionally, the developed algorithm is robust against most attacks, such as distinguishing attack and can be used in different protocols such as Secure Sockets Layer (SSL) Protocol, Oracle Secure SQL, and Wired Equivalent Privacy (WEP) Protocol.