karpathy / cryptos

Just me developing a pure Python from-scratch zero-dependency implementation of Bitcoin for educational purposes, including all of the under the hood crypto primitives such as SHA-256 and elliptic curves over finite fields math.

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:

getnewaddress.py is a cli entryway to generate a new Bitcoin secret/public key pair and the corresponding (base58check compressed) address:

Bitcoin transaction objects (both legacy or segwit) can be instantiated and parsed from raw bytes. An example of parsing a legacy type transaction:

This isn't exactly a complete verification as a Bitcoin full node would do and e.g. skips verification of double spends, script sizing limits, etc., and also it only supports the (simpler) p2pkh transactions. Notably, this does not include the "modern" segwit versions used predominantly in today's Bitcoin traffic since the soft fork of BIP141 around July 2017.

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