Empty string hash and null char hash are not same?

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I'm using hashlib sha256 (python) to prove two input.

My hypotesis was null char and empty string will give same hash.

Here my code

from hashlib import sha256
print(sha256(b'\x00').hexdigest(),end='\n\n')
print(sha256(b'').hexdigest())

And it gave output

6e340b9cffb37a989ca544e6bb780a2c78901d3fb33738768511a30617afa01d

e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855

Why they dont gave same result?

Is there relation with C language string format which the string always end with null? So when i hash null, it will hash double null?

hash
1 Answers

An empty string is (or, strictly speaking, "encodes to") a byte array of length zero, containing no bytes. You can observe this e.g. as follows, using Python:

>>> list(bytes("", 'ascii'))
[]

A string consisting of a single zero-byte on the other hand is a byte array of length one, containing a single byte of value zero:

>>> list(bytes("\x00", 'ascii'))
[0]

As such these two inputs are different, and will hash to different values.

As was mentioned in comments above, there is no relation to how some languages such as C represent strings, using a zero-byte to indicate their end.

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