SHA (Secure Hash Algorithm，译作安全散列算法) 是美国国家安全局 (NSA) 设计，美国国家标准与技术研究院 (NIST) 发布的一系列密码散列函数。正式名称为 SHA 的家族第一个成员发布于 1993年。然而现在的人们给它取了一个非正式的名称 SHA-0 以避免与它的后继者混淆。两年之后， SHA-1，第一个 SHA 的后继者发布了。 另外还有四种变体，曾经发布以提升输出的范围和变更一些细微设计: SHA-224, SHA-256, SHA-384 和 SHA-512 (这些有时候也被称做 SHA-2)。-SHA (Secure Hash Algorithm, translated as Secure Hash Algorithm) is the design of the U.S. National Security Agency (NSA), the U.S. National Institute of Standards and Technology (NIST) released a series of cryptographic hash function. The official name for a member of the SHA family, was released in 1993. However, people now give it an informal name of SHA-0 to avoid confusion with its successor. Two years later, SHA-1, the first SHA successor release. In addition there are four variants, once released in order to enhance the range of the output and change some subtle design: SHA-224, SHA-256, SHA-384 and SHA-512 (these are sometimes called SHA-2).