The RC5 encryption algorithm, developed by Ronald L. Rivest, is a fast symmetric block cipher designed for both hardware and software implementations. It features variable word size, variable number of rounds, and a variable-length secret key. RC5 is notable for its use of data-dependent rotations, where the rotation amount is determined by the low-order bits of another intermediate result. This feature enhances the algorithm's cryptographic strength and makes it adaptable to different processor word lengths. RC5 is parameterized by three main values: word size $w$, number of rounds $r$, and key length $b$. The algorithm uses an expanded key table $S$, derived from the secret key, which is used in both encryption and decryption processes. The encryption process involves a series of rounds where data is transformed using rotations, XOR operations, and additions from the key table. Decryption is the inverse process, involving right rotations and subtraction from the key table. RC5's design emphasizes simplicity, efficiency, and adaptability. It is implemented in a compact manner, suitable for various platforms, including smart cards. The algorithm's flexibility allows users to adjust parameters based on their specific security and performance requirements. RC5's use of data-dependent rotations is a key innovation, contributing to its cryptographic strength and making it resistant to certain types of cryptanalysis, such as differential and linear cryptanalysis. The article also provides a reference implementation of RC5-32/12/16 in C, demonstrating its practical application. The implementation shows that RC5 can be efficiently executed on various processors, with performance varying based on hardware capabilities. The article concludes with a call for further analysis and testing to determine the full security strength of RC5, highlighting its potential as a robust encryption algorithm.The RC5 encryption algorithm, developed by Ronald L. Rivest, is a fast symmetric block cipher designed for both hardware and software implementations. It features variable word size, variable number of rounds, and a variable-length secret key. RC5 is notable for its use of data-dependent rotations, where the rotation amount is determined by the low-order bits of another intermediate result. This feature enhances the algorithm's cryptographic strength and makes it adaptable to different processor word lengths. RC5 is parameterized by three main values: word size $w$, number of rounds $r$, and key length $b$. The algorithm uses an expanded key table $S$, derived from the secret key, which is used in both encryption and decryption processes. The encryption process involves a series of rounds where data is transformed using rotations, XOR operations, and additions from the key table. Decryption is the inverse process, involving right rotations and subtraction from the key table. RC5's design emphasizes simplicity, efficiency, and adaptability. It is implemented in a compact manner, suitable for various platforms, including smart cards. The algorithm's flexibility allows users to adjust parameters based on their specific security and performance requirements. RC5's use of data-dependent rotations is a key innovation, contributing to its cryptographic strength and making it resistant to certain types of cryptanalysis, such as differential and linear cryptanalysis. The article also provides a reference implementation of RC5-32/12/16 in C, demonstrating its practical application. The implementation shows that RC5 can be efficiently executed on various processors, with performance varying based on hardware capabilities. The article concludes with a call for further analysis and testing to determine the full security strength of RC5, highlighting its potential as a robust encryption algorithm.