The sha1 hash is a cryptographic hash function algorithm that is invented by NSA of US(national security Agency of united states) and published to the public by the US National Institute of Standards and Technology as a Federal Information Processing Standard.http://onlinetoolsland.com/sha1-hash-sha256-hash-sha512-hash/
The sha1 hash is used in many modern security protocols and applications, such as TLS,SSH, IPsec ,PGP and etc, beside security applications and protocols sha1 hash is also used to generate unique identifier in many user applications to identify revisions, or used as a checksum for data integrity.
In united states ,it is required by law that certain US government applications must use the sha hash algorithm inside them, such as cryptographic protocols and algorithms to prevent information leaks. many enterprises also use the sha1 hash algorithm in their application, products or daily work.
The sha-2 hash algorithm(include sha256 hash and hash 512 hash) is designed by NSA in 2001. The sha-2 algorithm works the same as sha-1 which use a serials of digital bits and produce a fixed length of hashed value. People can use the sha-2 algorithm as a checksum for digitial data.
Although SHA2 hash(sha256 hash and sha512 hash) has some similarity to the SHA1 hash algorithm, there is not a partially useful attacks on sha-2. As the time of writing, the best public attacks break preimage resistance for 52 rounds on SHA256 hash or 57 rounds on SHA512 hash, and collision resistance for 46 rounds of SHA256 hash, Only the collision attacks are of practical complexity; none of the attacks extend to the full round hash function.People now find that SHA256 hash and SHA512 hash algorithm , and to a lesser degree, the SHA-224 and SHA-384 are prone to length extension attacks, make it insecure for ceratin applications.
The original sha1 hash is designed as a part of Capstone project , which is a US government long term to develop cryptography standards for public and government use. The sha1 algorithm is designed to produce a message digest by using the similar principles as the MD4 and MD5 message digest algorithms.in fact both sha and md5 are came from MD4. But the sha hash algorithm’s design is more conservative.
As the time of writing , there are 4 generations in the sha hash family , they are the sha-0 (sha0) hash, sha-1(sha1 hash) hash, sha-2(sha2 hash include sha256 hash and sha512 hash)hash ,and sha-3(sha3 hash) hash. we will talk about each of the hash algorithm In detail.