SaludID Plus — The Sovereign Identity Ring

// Master key generated at ring setup using hardware entropy — NEVER leaves chip
MasterKey = HMAC-SHA512("SaludIDPlus", ring_hardware_entropy)

// Hardened child keys (apostrophe = hardened = BIP-32 index + 2^31)
// A leaked child key + parent xPub CANNOT reconstruct any sibling or parent key
P0_key = CKDpriv(MasterKey, 44'/7231'/0')   // Healthcare
P1_key = CKDpriv(MasterKey, 44'/7231'/1')   // Financial
P2_key = CKDpriv(MasterKey, 44'/7231'/2')   // Credentials
P3_key = CKDpriv(MasterKey, 44'/7231'/3')   // Recovery

// Per-partition purpose sub-keys (also hardened)
P0_sign_key   = CKDpriv(P0_key, 0')   // Signs W3C Verifiable Presentations for CVS/CMS
P0_enc_key    = HKDF(P0_key,  "P0_ENC_v1")   // AES-256-GCM encrypts P0 data on chip + IPFS

P2_fido2_key  = CKDpriv(P2_key, 0')   // FIDO2/WebAuthn CTAP2 authenticator key
P2_ssh_key    = CKDpriv(P2_key, 1')   // Ed25519 SSH signing key (deterministic)
P2_gpg_key    = CKDpriv(P2_key, 2')   // GPG / code-signing certificate key
P2_api_key    = HKDF(P2_key,  "P2_API_v1")   // AES-256 encrypts stored API keys in IPFS vault

// ISOLATION GUARANTEE (mathematical, not policy):
// Know P1_key + MasterKey extended public key? Cannot derive P0, P2, P3, or MasterKey.
// CVS/Aetna receive: ZK proof signed by P0_sign_key only. Zero key material shared.
// Partitions 1/2/3 existence: cryptographically undetectable from P0 ZK proof.

struct PartitionCommitment {
  bytes32 commitmentHash;  // keccak256(partition || ring_addr || data_hash || nonce)
  uint64  lastUpdated;     // Unix timestamp of last partition data update
  uint8   schemaVersion;   // Credential schema version (forward compatibility)
  bool    active;          // Is this partition provisioned?
}

struct IdentityRecord {
  PartitionCommitment p0_healthcare;  // P0: only partition with authorized access

  // P1/P2/P3: existence not publicly confirmable — double-blinded
  bytes32 p1_blinded;  // keccak256(P1_commitment || ring_salt) — unlinkable to content
  bytes32 p2_blinded;  // keccak256(P2_commitment || ring_salt)
  bytes32 p3_blinded;  // keccak256(P3_commitment || ring_salt)

  address ringAddress;      // Tangem ring's ERC-4337 smart account address
  bytes32 ringFingerprint;  // keccak256(ring_public_key) — verifies hardware binding
  bool    premiumTier;      // True = all 4 partitions active
}

// P0 healthcare ZK verification — the ONLY function external partners can call
function verifyHealthcareCredential(
  uint256 tokenId,
  bytes   calldata zkProof,       // ZK: "ring holds valid P0 credential matching commitment"
  bytes32          requestedClaim // Which claim (e.g. "medicare_part_b_enrolled")
) external view returns (bool valid, uint64 proofExpiry) {
  PartitionCommitment storage p0 = identities[tokenId].p0_healthcare;
  require(p0.active, "P0 not provisioned");
  valid = IZKVerifier(zkVerifier).verifyPartitionClaim(
    p0.commitmentHash, requestedClaim, zkProof
  );
  proofExpiry = uint64(block.timestamp) + 900; // 15-minute proof window
}

// P1/P2/P3: NO public function exists to confirm their state or content
// Private partition access: ring holder only, via NFC signing session

// ERC-5192 lock — SaludID Plus is NEVER transferable
function locked(uint256) external pure returns (bool) { return true; }

// Guardian recovery — P3 unlock after absence period + 3-of-5 shard quorum
function initiateGuardianRecovery(uint256 tokenId, bytes32[3] calldata shards) external {
  require(block.timestamp > identities[tokenId].lastActivity + ABSENCE_THRESHOLD);
  // Validate Shamir reconstruction, emit RecoveryInitiated, off-chain P3 decrypt begins
}

def credential_request_flow(service_name, cred_type):
    # 1. Agent intercepts service request (git push, aws s3 ls, docker push)
    challenge = generate_challenge(service_name, cred_type)

    # 2. Send NFC challenge to ring via phone BLE bridge
    #    User sees notification: "Tap ring to approve AWS credentials"
    ring_sig = tangem_sdk.sign_nfc(challenge, partition=2,
                                    path="m/44'/7231'/2'/0'")

    # 3. Derive AES-256-GCM decryption key from ring signature + service context
    dk = HKDF(ring_sig.signature, label="P2_API_" + service_name)

    # 4. Fetch + decrypt credential from IPFS encrypted vault
    enc_cred = ipfs.get(P2_vault_manifest[service_name])
    credential = AES256GCM.decrypt(enc_cred, dk)

    # 5. Inject into OS session for exactly 15 minutes, then wipe
    inject_to_os_keychain(credential, ttl_seconds=900)

    # Credential NEVER saved to disk. NEVER in shell history. NEVER in clipboard.
    # If ring is removed from proximity, session immediately revoked.