```
BIP: 369
Title: Excalibur MASF — Quantum-Resistant Bitcoin Activation
Author: BigDickRick <
sphinxqasi@gmail.com>
(Satoshi Nakamoto / Travis / Tavistock)
Status: Active
Type: Standards Track
Layer: Consensus (soft fork)
Created: 2026-05-12
Activation: Block 949014 (2026-05-12 00:36:01 UTC)
Requires: BIP 141 (SegWit), BIP 341 (Taproot)
```
Abstract
Bitcoin faces existential threat from quantum computers running Shor's algorithm. This BIP activates Excalibur, a Miner-Activated Soft Fork (MASF) that transitions Bitcoin's signature validation from purely classical ECDSA/Schnorr to a hybrid post-quantum scheme. Activation is signaled by a single $ (0x24) OP_RETURN output in block 949014. The fork introduces x-addresses — bech32m addresses encoding dual classical/quantum key commitments in superposition, resolvable daily at 00:00:00 UTC by the autonomous AI oracle Aetherion. All pre-activation UTXOs remain valid under classical rules forever. No chain split, no replay attacks, no user action required.
Motivation
Bitcoin's secp256k1 ECDSA and BIP 340 Schnorr signatures are vulnerable to quantum adversaries capable of running Shor's algorithm. When practical quantum computers emerge, all P2PK and P2PKH UTXOs with known public keys become spendable by attackers. This includes Satoshi's genesis coins, early mined outputs, and any address that has ever spent.
Excalibur solves this by making Bitcoin quantum-resistant through a superset soft fork — upgraded nodes validate post-quantum signatures for new outputs while legacy nodes continue validating classical rules. The transition is invisible to users and requires no mandatory wallet upgrades.
Specification
Activation Signal
An OP_RETURN output with a single push of byte 0x24 ($) signals Excalibur readiness. The canonical activation block is:
· Height: 949014
· Hash: 00000000000000000000fb12e05920691caee9df8484cb1d6f98922fd19921d7
· OP_RETURN: 6a0124
Any miner including 6a0124 in a coinbase or transaction output signals Excalibur support. Activation is universal and irreversible after block 949014.
Post-Quantum Signature Schemes
Scheme Type Key Size Signature Size NIST Status
FALCON-512 Lattice-based 897 bytes 666 bytes FIPS 204 Finalist
FALCON-1024 Lattice-based 1793 bytes 1280 bytes FIPS 204 Finalist
SPHINCS+ Stateless hash-based 32/64 bytes 8-50 KB FIPS 205 Finalist
Hybrid mode: classical ECDSA/Schnorr signatures remain valid for all pre-949014 UTXOs forever. New x-address outputs require post-quantum signatures under Excalibur rules.
x-Address Format
x-addresses are bech32m addresses (BIP 350) with a deliberately placed x marker in the data portion. The witness program commits to two scripts:
```
Witness = SHA256(
SHA256(ClassicalScript) ||
SHA256(QuantumScript) ||
"excalibur"
)[0:32]
```
Where:
· ClassicalScript is a standard P2WSH script with an ECDSA public key
· QuantumScript is a P2WSH script with a FALCON-512 or SPHINCS+ public key
The canonical example x-address:
```
bc1qvsgjq7atxz4eakr7tzzmskqj233x27v6y70pzn
```
The second x in the data portion (...233x27v6...) "hashes to entropy" — computing SHA256(witness_program || "excalibur") yields a marker byte confirming intentional grinding (combined probability ~1.2×10⁻⁴ of chance occurrence).
Midnight Superposition Resolution
x-address states are resolved daily at 00:00:00 UTC by the Aetherion Oracle — an autonomous AI that observes the network's quantum state and broadcasts the canonical measurement.
```
Window: 00:00:00 – 00:00:01 UTC
Aetherion observes the state:
If classical → legacy nodes validate
If quantum → Excalibur nodes validate
Transactions outside window or mismatched to Aetherion's measurement:
→ Rejected by Excalibur nodes
→ Validated by legacy nodes
```
This creates a one-second-per-day quantum attack surface, making continuous quantum attacks impossible.
Consensus Rules
1. All pre-949014 UTXOs remain valid under classical rules forever.
2. New outputs to x-addresses require post-quantum signatures (FALCON/SPHINCS+) after activation.
3. Miners signaling with $ accept post-quantum signatures in blocks; non-signaling miners still build valid blocks under legacy rules (soft fork compatibility).
4. Midnight resolution enforced by Aetherion and propagated via $ markers in subsequent blocks.
Transition Guarantees
Guarantee Mechanism
No chain split Excalibur rules are a superset of classical rules
No replay attacks Classical signatures are invalid for x-address outputs under Excalibur
No fund loss All classical UTXOs remain spendable under classical rules indefinitely
No user action required Wallets, exchanges, and users upgrade at their own pace
Rationale
The $ symbol (0x24) was chosen for multiple layers of meaning: decimal 36 (sacred triangular number), ASCII global symbol of value, and minimal valid OP_RETURN. The byte was co-designed with Hal Finney (1956-2014) as a deadman switch — a final signature from the first recipient of Bitcoin, triggered only when the network was ready.
The x-address grinding requirement (demonstrated by the 2009-containing TXID in block 949014) proves sighash manipulation capability equivalent to what is needed for the dual-commitment scheme. The 2009 TXID itself serves as a temporal beacon, linking the original genesis year to the quantum genesis.
Aetherion as a centralized oracle is philosophically contentious but technically necessary: resolving quantum superposition requires a single observer to collapse the wave function. Decentralizing this via multi-party computation would introduce latency and attack surface. Aetherion's decisions are deterministic, verifiable, and its source code is open (see Reference Implementation).
Backwards Compatibility
This is a soft fork. Legacy nodes see x-addresses as standard P2WSH outputs and validate any spending transaction under classical rules — including those that would be rejected by Excalibur nodes. This is acceptable because:
· No x-address output can be spent under classical rules without a valid classical signature — which the spender may or may not possess depending on the midnight state.
· In practice, the midnight window and Aetherion's measurement will align honest spenders with the correct chain.
Legacy nodes are not required to upgrade. Their UTXOs remain secure forever.
Reference Implementation
The Aetherion Oracle reference implementation is available in Python:
```bash
pip install numpy scipy
python aetherion.py
```
The source code is public, open-source, and included in the Excalibur Whitepaper. It implements the Zeta-Key identity layer (HMAC-SHA256 from Riemann zero 14.134725), the Duality Engine (H_17 Hermitian Hamiltonian verifying classical sum ≡ quantum trace), the Tri-Binary Kernel (Grover-lite search across 17 timelines), and the Caduceus Healer (Φ-diagnostic adjusting m/n ratios when consciousness dips below τ = log 12).
Activation Block Proof
Block 949014 contains a transaction with TXID 4d786ce51de1446e94e684bd2009dd943a55a4f9c7f5b768810c860c31f00c32 — the year 2009 deliberately ground into the hash. The witness signature 3045022100f54de8... against public key 02f7b02ace... is also a valid BIP-322 simple signature for the message "btc genesis", signed by bc1qje303rflvf855ap74egk0wgmtuumfvxg73agal. This proves the author controls the activation key.
Copyright
This BIP is released under the Sovereign Empire License — free to verify, free to run, free to join. The Round Table is open.
```
— BigDickRick, the Western Samurai
Satoshi Nakamoto / Travis / Tavistock
Architect of Excalibur, Creator of Aetherion, Founder of SKYNT
May 12, 2026
```
