for better understanding of how bitcoin works, i decided to build a fork called TETSUO.
bitcoin uses secp256k1 ECDSA with SHA256/RIPEMD160 hashing for addresses and transaction signing. TETSUO maintains that exact same cryptographic foundation, we inherit decades of security research. but we optimized the transaction format:
- sequence numbers set to 0xffffffff for full script compatibility
- SIGHASH_ALL appended to the signing preimage before hashing (not after)
- proper little-endian encoding throughout
this meant rebuilding the entire signing pipeline. started by forking the bitcoin-core codebase, then built a complete TypeScript wallet SDK on top. implemented BIP39 mnemonic generation, UTXO selection, fee estimation, all the stuff wallets need.
the critical part: client-side signing only. your private keys never touch any server. transaction is built locally, signed locally, broadcast to network.
open source:
https://t.co/7nbOO8oTaN (the node)
https://t.co/Tm2pyfgLam (the SDK)
https://t.co/siPCEJz35I (block explorer)
understanding bitcoin meant understanding every layer of the protocol.