What is SHA-1?

SHA-1 (Secure Hash Algorithm 1) is a cryptographic hash function that produces a 160-bit (20-byte) hash value, typically displayed as 40 hexadecimal characters. Published by the National Security Agency (NSA) in 1995, SHA-1 was widely used for digital signatures and certificates. In 2017, researchers demonstrated a practical collision attack, and major browsers now deprecate SHA-1 for TLS certificates. While still used in some legacy systems, SHA-256 or SHA-3 are recommended for new applications requiring cryptographic security.