security.md

tags	cyber, cip
crystal-type	entity
crystal-domain	cyber
status	draft

nox security

security properties and formal guarantees of [[nox]]

security bounds

SOUNDNESS:       Invalid transactions rejected with probability ≥ 1 - 2^(-128)
PRIVACY:         Cannot distinguish transactions with same public structure
CONSERVATION:    Σ(energy) = initial + minted - burned (mathematically enforced)
QUANTUM RESIST:  Hash-based security only, ~128-bit post-quantum (Grover limit)

attack surface

Attack          │ Defense
────────────────┼─────────────────────────────────────────────
Double Spend    │ Nullifier set prevents reuse
Inflation       │ Circuit enforces conservation
Front-Running   │ Privacy hides transaction contents
Sybil           │ Focus proportional to stake
DoS             │ Focus-based metering limits computation
Eclipse         │ Namespace completeness proofs
Replay          │ Nonces and nullifiers ensure uniqueness
Forgery         │ ZK proofs unforgeable without witness

formal properties

Turing completeness

Theorem: nox is Turing-complete. Proof: Construct encoding of arbitrary Turing machine M via patterns 0-4, 9. ∎

confluence

Theorem: nox is confluent. Proof: Orthogonal rewrite system by Huet-Levy (1980). ∎

cost determinism

Theorem: Cost is identical across all reduction orders and implementations. Proof: By structural induction on formula. ∎

focus conservation

Theorem: $\sum_i \text{focus}(i) = 1$ for all valid states. Proof: All operations preserve sum; invalid transitions rejected by verification. ∎

privacy soundness

Theorem: A valid ZK proof implies all circuit constraints are satisfied with probability $\geq 1 - 2^{-128}$. Proof: By [[zheng]] soundness. ∎

double-spend prevention

Theorem: Same record cannot be spent twice. Proof:

1. Each record has unique (nonce, owner_secret) pair
2. Nullifier = H(nonce, owner_secret) is deterministic
3. Same record → same nullifier
4. Nullifier set is append-only
5. Transaction rejected if nullifier already in set ∎

complexity comparison

┌─────────────────────┬───────────────┬───────────────┬───────────────┬───────────────┐
│     Operation       │  Traditional  │  Blockchain   │   Database    │     nox       │
│                     │  (RAM model)  │  (Ethereum)   │  (SQL/NoSQL)  │               │
├─────────────────────┼───────────────┼───────────────┼───────────────┼───────────────┤
│ Equality check      │ O(n) compare  │ O(n) compare  │ O(n) compare  │ O(1) hash     │
│ Membership proof    │ O(n) scan     │ O(log n) MPT  │ O(log n) index│ O(log² n) poly│
│ Completeness proof  │ impossible    │ impossible    │ impossible    │ O(log² n) poly│
│ Computation verify  │ O(n) re-exec  │ O(n) re-exec  │ N/A           │ O(log n) zheng│
│ Recursive verify    │ O(n) re-exec  │ O(n) re-exec  │ N/A           │ O(1) composed │
│ Privacy + verify    │ incompatible  │ incompatible  │ incompatible  │ O(1) ZK proof │
├─────────────────────┼───────────────┼───────────────┼───────────────┼───────────────┤
│ Cost determinism    │ ✗ cache-dep   │ ~ gas approx  │ ✗ query-dep   │ ✓ structural  │
│ Parallel safety     │ ✗ explicit    │ ✗ sequential  │ ✗ locks       │ ✓ confluent   │
└─────────────────────┴───────────────┴───────────────┴───────────────┴───────────────┘

see [[cyber/nox]] for the execution model, [[cyber/bbg]] for the ZK privacy architecture, [[zheng]] for proof verification