Hash Functions - Examples - Practical Cryptography for Developers

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Hash Functions - Examples
In this section we shall provide a few examples about calculating cryptographic hash functions in Python.
Calculating Cryptographic Hash Functions in Python
We shall use the standard Python library hashlib. The input data for hashing should be given as bytes sequence (bytes object), so we need to encode the input string using some text encoding, e.g. utf8. The produced output data is also a bytes sequence, which can be printed as hex digits using binascii.hexlify() as shown below:
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import hashlib, binascii
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​
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text = 'hello'
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data = text.encode("utf8")
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​
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sha256hash = hashlib.sha256(data).digest()
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print("SHA-256:   ", binascii.hexlify(sha256hash))
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​
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sha3_256 = hashlib.sha3_256(data).digest()
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print("SHA3-256:  ", binascii.hexlify(sha3_256))
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​
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blake2s = hashlib.new('blake2s', data).digest()
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print("BLAKE2s:   ", binascii.hexlify(blake2s))
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​
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ripemd160 = hashlib.new('ripemd160', data).digest()
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print("RIPEMD-160:", binascii.hexlify(ripemd160))
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Run the above code example: https://repl.it/@nakov/Hashes-SHA2-SHA3-BLAKE2-RIPEMD-in-Python.
The expected output from the above example looks like this:
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SHA-256:    b'2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824'
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SHA3-256:   b'3338be694f50c5f338814986cdf0686453a888b84f424d792af4b9202398f392'
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BLAKE2s:    b'19213bacc58dee6dbde3ceb9a47cbb330b3d86f8cca8997eb00be456f140ca25'
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RIPEMD-160: b'108f07b8382412612c048d07d13f814118445acd'
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Calculating Keccak-256 hashes (the hash function used in the Ethereum blockchain) requires non-standard Python functions. In the below example we use the pycryptodome package available from PyPI: https://pypi.org/project/pycryptodome.
First install "pycryptodome" (https://www.pycryptodome.org)
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pip install pycryptodome
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Now write some Python code to calculate a Keccak-256 hash:
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from Crypto.Hash import keccak
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import binascii
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​
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keccak256 = keccak.new(data=b'hello', digest_bits=256).digest()
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print("Keccak256:", binascii.hexlify(keccak256))
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Run the above code example: https://repl.it/@nakov/Keccak256-in-Python.
The output from the above examples is:
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Keccak256: b'1c8aff950685c2ed4bc3174f3472287b56d9517b9c948127319a09a7a36deac8'
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Secure Hash Algorithms
Exercises: Calculate Hashes
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Calculating Cryptographic Hash Functions in Python