SHA-256 is a family of cryptographic functions SHA-2. It was designed by the National Security Agency (NSA) and was published in 2001 by the National Institute of Standards and Technology (NIST) as a federal information processing standard for the United States government. SHA is the Secure Hash Algorithm. SHA-2 includes a number of changes that distinguish it from its predecessor (SHA-1). SHA-2 is composed of a set of four functions offering shortcuts to 224, 256, 384 or 512 bits. In 2005, vulnerabilities of SHA-1 were identified and it was found that SHA-1 is too weak and stronger hash functions are needed. Although SHA-2 bears some resemblance to the SHA-1 algorithm, these attacks have not been effectively extended to SHA-2. In 2012, the new standard SHA-3 was chosen. NIST published four additional hash functions of the SHA family and named them according to their hash length (in bits): SHA-224, SHA-256, SHA-384 and SHA-512. These algorithms are collectively known as SHA-2. SHA-256 and SHA-512 were proposed for use in DNSSEC. Unix and Linux suppliers tend to use the 256-and 512-bit SHA-2 for secure password hashing. NIST directive says that American government agencies must stop using SHA-1 after 2010 and the finalization of the SHA-3 may accelerate the migration from SHA-1. The SHA-2 is implemented in some commonly used security applications and protocols, including TLS, SSL, PGP, SSH, S / MIME, and IPsec Bitcoin. SHA-1 and SHA-2 are safe algorithms required by law to be used in some applications (e.g. the United States government uses cryptographic algorithms and protocols to protect sensitive information). FIPS PUB 180-1 also encourages the implementation and use of SHA-1 by private and commercial organizations. SHA-1 ceases to be used for most of government applications; American National Institute of Standards and Technology recommends: "Federal agencies should immediately stop using SHA-1 for applications that require resistance to collisions, while after 2010 must use a family of hash functions SHA-2 for these uses" (emphasis in original).