FHE Demo Programs

Seven runnable demos demonstrating Fully Homomorphic Encryption use cases for digital securities.

Prerequisites

cd ~/work/lux/fhe
go build ./...   # verify the fhe package compiles

Demos

1. Dark Pool (Encrypted Order Matching)

Traders submit encrypted limit orders. The matching engine compares bids against asks homomorphically. Only matched fills are decrypted.

go run ./cmd/demos/darkpool

2. Programmable Compliance

Verifies SEC diversification rules on an encrypted portfolio: no single position > 25%, total exposure < 80%. Only the boolean compliance result is revealed.

go run ./cmd/demos/compliance

3. Private Market Making

Three market makers submit encrypted bid/ask quotes. Best bid (highest) and best ask (lowest) are selected via encrypted comparisons. Losing quotes stay private.

go run ./cmd/demos/marketmaker

4. Encrypted Sealed-Bid Auction

Five participants submit encrypted bids. The winner is determined via tournament-style max comparisons. Only the winning bid is decrypted.

go run ./cmd/demos/auction

5. Private Shareholder Voting

100 shareholders vote encrypted yes/no. Votes are tallied using a ripple-carry adder (XOR + AND gates). Only the final count is decrypted.

go run ./cmd/demos/voting
go run ./cmd/demos/voting -voters 50 -yes 30

6. Confidential NAV

An ETF's encrypted holdings (10 positions with share counts and prices) are used to compute NAV = sum(shares * price) / totalShares. Only the final NAV is revealed.

go run ./cmd/demos/nav

7. Compliance Proof

Proves two conditions on an encrypted portfolio: max position < 25% and no sanctioned counterparty. Outputs plaintext booleans while inputs stay encrypted.

go run ./cmd/demos/proof

Run All

for d in darkpool compliance marketmaker auction voting nav proof; do
  echo "=== $d ==="
  go run ./cmd/demos/$d
  echo
done

Architecture

All demos use the github.com/luxfi/fhe package with boolean circuit evaluation:

Parameters: PN10QP27 (128-bit security, N=1024)
Boolean gates: Evaluator with AND, OR, XOR, NOT, ANDNY, MAJORITY + bootstrapping
Encryption: Encryptor.Encrypt(bool) encrypts individual bits
Decryption: Decryptor.Decrypt(*Ciphertext) decodes bits (secret key holder only)
Integers: 8-bit values represented as [8]*Ciphertext (bit-decomposed, LSB first)
Comparison: MSB-first bitwise less-than circuit using ANDNY + XOR + AND + OR
Addition: Ripple-carry full adder using XOR + MAJORITY

FHE operations run without the secret key. The evaluator uses bootstrap keys (public) for noise management via programmable bootstrapping after each gate.

Performance (Apple M-series, PN10QP27)

Key generation: ~600ms-1s (one-time)
Encryption: ~5ms per 8-bit value (8 bit encryptions)
Single gate (AND, OR, XOR): ~400-600ms per gate
8-bit comparison (lt/gt/ge): ~12-16s (24 gates: 8x ANDNY + 8x XOR + 7x AND + 7x OR)
8-bit addition: ~10-13s per add (24 gates: 8x XOR + 8x XOR + 8x MAJORITY)
Vote tally (1 ballot): ~5.8s (14 gates: 7x XOR + 7x AND for 7-bit accumulator)

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