SHA-1, or Secure Hash Algorithm 1, is a cryptographic hash function designed by the National Security Agency (NSA) in the 1990s. It produces a 160-bit hash value, typically rendered as a 40-digit hexadecimal number. SHA-1 is commonly used for data integrity verification and digital signatures. Despite its widespread use, SHA-1 has vulnerabilities that make it less secure over time. In 2017, researchers demonstrated practical collision attacks, where two different inputs produce the same hash. As a result, many organizations are transitioning to more secure alternatives like SHA-256 and SHA-3.