cryptos

Just me developing a pure Python from-scratch zero-dependency implementation of Bitcoin for educational purposes. This includes a lot of the core crypto math primitives such as SHA-256 and elliptic curves over finite fields math (but with the exception of RIPEMD160 hash function, which I imported).

SHA-256

My pure Python SHA-256 implementation closely following the NIST FIPS 180-4 spec, in cryptos/sha256.py. Since this is a from scratch pure Python implementation it is slow and obviously not to be used anywhere except for educational purposes. Example usage:

$ echo "some test file lol" > testfile.txt
$ shasum -a 256 testfile.txt
4a79aed64097a0cd9e87f1e88e9ad771ddb5c5d762b3c3bbf02adf3112d5d375
$ python -m cryptos.sha256 testfile.txt
4a79aed64097a0cd9e87f1e88e9ad771ddb5c5d762b3c3bbf02adf3112d5d375

Keys

getnewaddress.py is a cli entryway to the code that generates a new Bitcoin private/public key pair and the corresponding (base58 compressed) address:

$ python getnewaddress.py
generated private key:
0xc322622e6a0033bb93ff666753f77cc8b819d274d9edea007b7e4b2af4caf025
corresponding public key:
x: 5B9D87FE091D52EA4CD49EA5CEFDD8C099DF7E6CCF510A9A94C763DE38C575D5
y: 6049637B3683076C5568EC723CF7D38FD603B88447180829BBB508C554EEA413
compressed bitcoin address (b58check format):
1DBGfUXnwTS2PRu8h3JefU9uYwYnyaTd2z

You can also generate your own entropy from keyboard timings if you call the cli as $ python getnewaddress.py user, or you can verify that the implementation is not broken by reproducing the Mastering Bitcoin Chapter 4 example:

$ python getnewaddress.py mastering
generated private key:
0x3aba4162c7251c891207b747840551a71939b0de081f85c4e44cf7c13e41daa6
corresponding public key:
x: 5C0DE3B9C8AB18DD04E3511243EC2952002DBFADC864B9628910169D9B9B00EC
y: 243BCEFDD4347074D44BD7356D6A53C495737DD96295E2A9374BF5F02EBFC176
compressed bitcoin address (b58check format):
14cxpo3MBCYYWCgF74SWTdcmxipnGUsPw3

Where we see that after the all crazy hashing and elliptic curve over finite fields gymnastics the bitcoin address 14cxpo3MBCYYWCgF74SWTdcmxipnGUsPw3 matches, phew :)

Digital Signatures

Elliptic Curve Digital Signature Algorithm (ECDSA) implemented in cryptos/ecdsa.py, example usage:

>>> from cryptos.ecdsa import sign, verify
>>> from cryptos.keys import gen_key_pair
>>> sk1, pk1 = gen_key_pair()
>>> sk2, pk2 = gen_key_pair()
>>> message = ('pk1 wants to pay pk2 1 BTC').encode('ascii')
>>> sig = sign(sk1, message)
>>> verify(pk1, message, sig)
True
>>> verify(pk2, message, sig)
False

Unit tests

$ pytest

License

MIT