BTC++ Riga 2025 hackathon submission

A lightning-fast Rust library for Bitcoin block height lookups using perfect hash functions, optimized for pre-BIP34 blocks (0-227,930).

• Perfect Hash Functions: Zero-collision lookups with minimal memory
• 18-bit Height Compression: Custom packing algorithm for memory efficiency
• Zero-Copy Deserialization: Using epserde for ultra-fast loading
• Feature-Gated Design: generate (building) and embedded (runtime) modes
• Self-Contained CLI: 908KB binary with embedded oracle data

Core Rust library with perfect hash implementation for Bitcoin block height lookups.

Ultra-minimal command-line tool for instant height lookups. Usage documentation: See delphi/README.md

• Lookup Speed: 2.5M+ lookups per second
• Memory Efficiency: 18-bit compressed heights
• Binary Size: 908KB self-contained executable
• Load Time: Instant (embedded data)

# Build the oracle data
cargo run --features generate --release

# Build the CLI tool
cd delphi
cargo build --release

# Test a lookup (Genesis block)
./target/release/delphi 000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f
# Output: 0

This repository now includes a simple RPC-based generator that queries your local bitcoind for all pre-BIP34 block hashes and writes them to assets/prebip34.txt.

Requirements:

• A running Bitcoin Core node with RPC enabled (e.g. -server=1)
• RPC credentials via either ~/.bitcoin/.cookie or -rpcuser/-rpcpassword

Usage:

# From the repo root
# By default reads ~/.bitcoin/.cookie and connects to http://127.0.0.1:8332
cargo run --example fetch_prebip34 --release

# Custom options:
#   --rpc-url       RPC endpoint (default http://127.0.0.1:8332)
#   --rpc-user      RPC username (else reads from ~/.bitcoin/.cookie)
#   --rpc-pass      RPC password (else reads from ~/.bitcoin/.cookie)
#   --cookie        Path to cookie file (default ~/.bitcoin/.cookie)
#   --concurrency   Number of parallel RPC calls (default 32)
#   --start-height  Start height (default 0)
#   --end-height    End height (default 227930)
#   --output        Output path (default assets/prebip34.txt)

# Example with explicit credentials and higher concurrency
cargo run --example fetch_prebip34 --release -- \
  --rpc-url http://127.0.0.1:8332 \
  --rpc-user myuser \
  --rpc-pass mypass \
  --concurrency 64

Once generated, you can build the oracle assets using:

cargo run --features generate --release

Note: marking version-2 headers with an x placeholder (so they can be handled separately) yields additional space savings. Compared to the naive approach, this optimization gives about 6.4% space savings.

Important: the boundary of 227,931 (exclusive) is sourced from Bitcoin Core's pre-BIP34 definition, but the oracle generated by this repository only includes blocks with header version == 1. Blocks with version == 2 are written as x placeholders by the generator and are intentionally skipped when building the perfect-hash; handle those blocks separately if you require full coverage.

• @ubbabeck
• @bayernator
• @FelixWeis
• Claude (AI Assistant) - Code architecture, optimization, and implementation