Hash
Cryptographic hash functions take arbitrary binary strings as input, and produce a random-like fixed-length output (called digest or hash value).
It is practically infeasible to derive the original input data from the digest. In other words, the cryptographic hash function is one-way (pre-image resistance).
Given the digest of one message, it is also practically infeasible to find another message (second pre-image) with the same digest (weak collision resistance).
Finally, it is infeasible to find two arbitrary messages with the same digest (strong collision resistance).
Regardless of the hash algorithm, an n bits long digest is at most as secure as a symmetric encryption algorithm keyed with n/2 bits (birthday attack).
Hash functions can be simply used as integrity checks. In combination with a public-key algorithm, you can implement a digital signature.
SHA-2
SHA-2 (Secure Hash Algorithm 2) is a set of cryptographic hash functions designed by the United States National Security Agency (NSA) and first published in 2001
입력
SHA-2 256 결과(hex)
SHA-2 512 결과(hex)