What are correlation attacks and algebraic attacks, and how do they exploit the vulnerabilities of single LFSRs?
Linear Feedback Shift Registers (LFSRs) are critical components in the design of stream ciphers used in classical cryptography. Their simplicity and efficiency make them attractive for generating pseudo-random sequences. However, despite these advantages, LFSRs are susceptible to various forms of cryptanalysis, including correlation attacks and algebraic attacks. These attacks exploit inherent vulnerabilities in LFSRs, compromising
- Published in Cybersecurity, EITC/IS/CCF Classical Cryptography Fundamentals, Stream ciphers, Stream ciphers and linear feedback shift registers, Examination review
Explain how the A5/1 cipher enhances security by using multiple LFSRs and non-linear functions.
The A5/1 cipher is a stream cipher used to provide encryption in the GSM (Global System for Mobile Communications) standard, which is widely used for mobile phone communications. The security of the A5/1 cipher is significantly enhanced by employing multiple Linear Feedback Shift Registers (LFSRs) and non-linear functions. This combination provides a robust mechanism for
How does an LFSR generate a key stream, and what role does the feedback polynomial play in this process?
A Linear Feedback Shift Register (LFSR) is a key component in the generation of pseudorandom sequences, which are important in stream ciphers for cryptographic applications. The LFSR generates a key stream by shifting bits through a register and using a feedback mechanism defined by a polynomial. This process is deterministic and relies heavily on the
What are the limitations of the one-time pad, and why is it considered impractical for most real-world applications?
The one-time pad (OTP) is a theoretically unbreakable cipher, provided certain conditions are met. It was first described by Frank Miller in 1882 and later independently reinvented by Gilbert Vernam in 1917. The fundamental principle behind the OTP is the use of a random key that is as long as the message itself, which is
How does a stream cipher differ from a block cipher in terms of data encryption?
Stream ciphers and block ciphers are two fundamental types of symmetric key encryption methods used in the field of cryptography to secure data. Both have distinct operational mechanisms and use cases, making them suitable for different scenarios. A stream cipher encrypts plaintext one bit or byte at a time, typically by combining it with a