p2pk-bf/CLAUDE.md

CLAUDE.md

This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.

Project purpose

Educational/research suite for studying Bitcoin P2PK (Pay-to-Public-Key) transactions and demonstrating why ECDSA secp256k1 bruteforce is computationally infeasible (keyspace 2^256). All docs and CLI output are in Italian. Two independent components share data via files, not code:

1. databases/ — Python scanner that walks the Bitcoin blockchain via the mempool.space API, finds P2PK outputs, stores them in SQLite, and checks UTXO spent/unspent status.
2. bruteforce/ — C++ program that loads target public keys and searches the private-key space for matches, as a performance demonstration (not a realistic attack — success probability is ~2^-256).

Data flows one way: scanner → SQLite DB (databases/bitcoin_p2pk_study.db) → extract_p2pk_utxo.py filters unspent P2PK → target_keys.txt → C++ bruteforce consumes it.

Commands

Python scanner (databases/)

python3 -m venv .venv && source .venv/bin/activate
pip install -r requirements.txt

cd databases
python3 scan_blockchain.py   # interactive: prompts for start/end block + delay
python3 view_db.py           # generates p2pk_report.html
python3 view_db.py --stats   # prints stats to terminal

C++ bruteforce (bruteforce/)

cd bruteforce
make install-deps      # apt packages: build-essential, libsecp256k1-dev, libgmp-dev, autoconf, libtool, pkg-config
make                   # builds secp256k1 locally from source if bruteforce/secp256k1/ doesn't exist (~5 min first time), then compiles p2pk_bruteforce
make clean             # remove binaries/object files
make clean-all         # also removes the locally-built secp256k1 tree
make debug             # -g -O0 build: p2pk_bruteforce_debug
make bench             # 10-second timed run
make pgo               # profile-guided optimization build (3-step: generate → run 30s → use)
make valgrind          # leak check on the debug build
make help              # list all targets

python3 extract_p2pk_utxo.py [db_path] [output.txt]   # default: ../databases/bitcoin_p2pk_study.db -> target_keys.txt
python3 extract_p2pk_utxo.py --stats                  # DB stats only, no extraction

./p2pk_bruteforce [target_keys.txt]   # runs until Ctrl+C; logs to progress.csv, matches to found_keys.txt

There is no test suite in this repo.

Architecture notes

bruteforce/p2pk_bruteforce.cpp (single file, everything lives here)

• One pthread per (core count − 1); each thread gets a disjoint slice of the 256-bit keyspace via partition_keyspace (only the top 64 bits are partitioned — the search relies on random start offsets within each thread's slice, not a full 256-bit range split).
• Target pubkeys are loaded from a .txt file (uncompressed hex, 04 prefix, one per line, header line skipped) into both an unordered_map<secp256k1_pubkey,...> (exact match) and a 64MB Bloom filter (fast negative rejection, checked first via check_match_fast).
• Performance trick: instead of computing privkey * G per candidate, it computes one EC multiplication then derives the next EC_BATCH_SIZE (256) keys via EC point addition against precomputed multiples of G (precompute_generator_multiples), which is much cheaper than repeated scalar multiplication.
• Build system auto-detects a local bruteforce/secp256k1/ (built by build_secp256k1.sh targeting this specific CPU with -march=native) and links against it via rpath instead of the system lib; falls back to system libsecp256k1/libgmp if absent.
• Matches are written to found_keys.txt; periodic throughput stats go to stdout and progress.csv every 10s.

databases/scan_blockchain.py

• P2PKBlockchainScanner class wraps all mempool.space API access (get_block_hash, get_block_transactions with pagination, check_utxo_status) and SQLite persistence.
• P2PK detection is deliberately redundant — a script is classified as P2PK if ANY of 4 independent checks match: explicit scriptpubkey_type, script byte length (67 or 35 bytes), ASM pattern (<pubkey> OP_CHECKSIG), or raw hex pattern (41<pubkey>ac / 21<pubkey>ac). This exists because the API's scriptpubkey_type field is not reliable for very old (pre-2012) P2PK outputs.
• Scanning is resumable: scan_progress table (single row, id=1) tracks last_scanned_block; reruns default to last_scanned_block + 1. UNIQUE(txid, output_index) on p2pk_addresses prevents duplicate inserts, so overlapping scan ranges are safe.
• This script and its SQLite DB/CSV outputs are intended to be committed and shared across contributors scanning different block ranges (see .gitignore — DB/CSV/HTML are NOT excluded).

bruteforce/extract_p2pk_utxo.py

• Reads only is_unspent = 1 rows from the scanner's DB, strips the 41.../21...ac script wrapper to get the raw pubkey, and re-adds the 04 prefix.
• Compressed pubkeys (33-byte, script length 70/hex prefix 21) are explicitly skipped — the C++ bruteforce only generates and matches uncompressed public keys.

Key coupling to be aware of

• The bruteforce binary's target file format (uncompressed hex pubkeys, 04 prefix, header line) is produced exclusively by extract_p2pk_utxo.py — if editing one side's format, update the other.
• Makefile CFLAGS use -march=native/-mtune=native and -ffast-math; binaries are not portable across different CPUs and should be rebuilt (make clean && make) after moving to different hardware.