SHA-256 belongs to the SHA-2 family of cryptographic hashes. It produces the 256 bit digest of a message.
>>> from Crypto.Hash import SHA256 >>> >>> h = SHA256.new() >>> h.update(b'Hello') >>> print h.hexdigest()
SHA stands for Secure Hash Algorithm.
Warning
SHA-256 is vulnerable to length-extension attacks, which are relevant if you are computing the hash of a secret message.
For instance, let's say you were planning to build a cheap MAC by concatenating a secret key to a public message m (bad idea!):
h = SHA-256(m||k)
By only knowing the digest h and the length of m and k, the attacker can easily compute a second digest h':
h′ = SHA-256(m||p||z)
where p is a well-known bit string and the attacker can pick a bit string z at will.
Crypto.Hash.SHA256