Lecture Notes: Secure Hash Algorithm (SHA) What is SHA? Secure Hash Algorithm (SHA) is a family of cryptographic hash functions designed by the National Security Agency (NSA) of the United States. SHA algorithms are used to generate a fixed-size hash value from a message of any length. This hash value can be used to verify the integrity of the message and detect any modifications or tampering. Common SHA Algorithms ● SHA-1: The original SHA algorithm, now considered insecure due to vulnerabilities. ● SHA-2: A family of secure hash algorithms, including SHA-256, SHA-384, and SHA-512. ● SHA-3: A more recent algorithm designed to replace SHA-2. How SHA Works 1. Padding: The input message is padded to a specific length before processing. 2. Initialization: A message digest is initialized with a fixed value. 3. Rounds: The message is processed through multiple rounds of a compression function. 4. Output: The final output is the hash value. Key Properties of SHA ● Deterministic: The same message will always produce the same hash value. ● Collision Resistance: It is computationally infeasible to find two different messages that produce the same hash value. ● One-Way Function: It is difficult or impossible to reverse the hashing process to obtain the original message from the hash value. Applications of SHA ● Digital Signatures: SHA is used to generate digital signatures, which can verify the authenticity and integrity of messages. ● Password Hashing: Passwords are often stored as hashed values using SHA algorithms to protect against unauthorized access. ● Data Integrity: SHA can be used to verify the integrity of data files and detect tampering. ● Checksums: SHA can be used as checksums to detect errors in data transmission. Conclusion SHA is a family of secure hash algorithms that are widely used in various applications. They provide a reliable and efficient way to verify the integrity of data and protect against unauthorized modifications. By understanding the principles of SHA, individuals and organizations can ensure the security of their digital information.