Secure Hash Algorithms (SHA) are cryptographic functions that take an input (or message) and produce a fixed-size string of characters, which is typically a sequence of numbers and letters. This output, known as a hash, is unique to each unique input, meaning even a small change in the input will result in a completely different hash. SHA is widely used in various security applications, including data integrity verification and digital signatures. There are several versions of SHA, including SHA-1, SHA-256, and SHA-3, each offering different levels of security and efficiency. These algorithms are essential in protecting sensitive information, ensuring that data has not been altered during transmission or storage.