Universal DID-Native Addressing (UDNA)

||    : Concatenation operator
⊕     : XOR operation  
H(x)  : Cryptographic hash function applied to x
Sig(sk, m) : Digital signature of message m using private key sk
Verify(pk, m, σ) : Signature verification using public key pk
KDF(k, c) : Key derivation function with key k and context c
A ⊕ B : XOR distance between identifiers A and B

Bit 0 (P): Pairwise flag - indicates PE-DID derived from PP-DID
Bit 1 (R): Rotation flag - message contains key rotation proof  
Bit 2 (E): Ephemeral flag - single-use DID, no state persistence
Bit 3 (A): Acknowledgment requested - requests transport-layer ACK
Bit 4 (K): Key pre-rotation hint - signals upcoming key rotation
Bits 5-15: Reserved for future use

// Node Identification (Sybil-resistant)
NodeID = BLAKE3(primary_verification_key_bytes)

// Distance Metric (XOR for efficient routing)
fn distance(a: NodeID, b: NodeID) -> NodeID {
    a ^ b
}

// Stored Values (Signed PeerInfo structures)
struct PeerInfo {
    did: String,
    multiaddrs: Vec,
    facets: Vec,
    timestamp: u64,
    signature: Vec,
}

struct FacetInfo {
    id: u8,
    capability: Option>,
}

#[derive(Debug, Error)]
pub enum UDNAError {
    #[error("DID resolution failed: {0}")]
    ResolutionFailed(String),
    
    #[error("Cryptographic operation failed: {0}")]
    CryptoError(#[from] CryptoError),
    
    #[error("Network error: {0}")]
    NetworkError(#[from] NetworkError),
    
    #[error("Protocol violation: {0}")]
    ProtocolError(String),
    
    #[error("Header validation failed: {0}")]
    HeaderValidationError(HeaderError),
    
    #[error("Key rotation in progress: {0}")]
    KeyRotationError(String),
    
    #[error("ZCAP verification failed: {0}")]
    ZCAPError(String),
}

// Automatic recovery strategies based on error type
impl UDNAError {
    pub fn recovery_strategy(&self) -> RecoveryStrategy {
        match self {
            UDNAError::ResolutionFailed(_) => RecoveryStrategy::RetryWithFallback,
            UDNAError::NetworkError(_) => RecoveryStrategy::Reconnect,
            UDNAError::KeyRotationError(_) => RecoveryStrategy::RefreshAndRetry,
            _ => RecoveryStrategy::FailFast,
        }
    }
}

pub enum DIDMethod {
    Key(did_key::KeyDID),
    Web(did_web::WebDID), 
    SCP(did_scp::SCPDID),
    ION(did_ion::IONDID),
    Unknown(String),
}

impl DIDMethod {
    pub async fn resolve(&self) -> Result {
        match self {
            DIDMethod::Key(did) => did.resolve_locally(),
            DIDMethod::Web(did) => did.resolve_via_https().await,
            DIDMethod::SCP(did) => did.resolve_via_dht().await,
            DIDMethod::ION(did) => did.resolve_via_bitcoin().await,
            DIDMethod::Unknown(_) => Err(ResolverError::UnsupportedMethod),
        }
    }
}

VARIABLES 
    cache,          \* Local DID document cache
    resolving,      \* Set of DIDs currently being resolved  
    network_state   \* Network connectivity status

Init == 
    /\ cache = [did \in DID |-> NULL]
    /\ resolving = {}
    /\ network_state = "connected"

Resolve(did) ==
    /\ did \notin resolving
    /\ resolving' = resolving \union {did}
    /\ \/ /\ cache[did] # NULL 
          /\ cache[did].ttl > Now()
          /\ RETURN cache[did].document
       \/ /\ QueryNetwork(did)
          /\ AWAIT NetworkResponse(did)

UpdateCache(did, document, ttl) ==
    /\ cache' = [cache EXCEPT ![did] = 
                  [document |-> document, ttl |-> ttl]]
    /\ resolving' = resolving \ {did}

AuthenticationIntegrity ==
    \A session \in Sessions :
        session.authenticated => 
            ControlsKey(session.peer_did, session.peer_key)

MessageOrdering ==
    \A s1, s2 \in SentMessages :
        /\ s1.session_id = s2.session_id
        /\ s1.sequence < s2.sequence
        => s1.timestamp <= s2.timestamp

ResolutionLiveness ==
    \A did \in ValidDIDs :
        <>[] (ResolveRequest(did) ~> ResolveResponse(did))

udna-address = "udna://" did-identifier ":" facet-id
did-identifier = "did:" method-name ":" method-specific-id
method-name = 1*method-char
method-char = %x61-7A / DIGIT  ; lowercase letters and digits
method-specific-id = *idchar
idchar = ALPHA / DIGIT / "." / "-" / "_"
facet-id = 1*3DIGIT  ; 0-255

{
  "test_name": "Basic DID Resolution and Validation",
  "input": {
    "did": "did:scp:z6MkhaXgBZDvotDkL5257faiztiGiC2QtKLGpbnnEGta2doK",
    "operation": "resolve_and_validate"
  },
  "expected_output": {
    "resolution_time": "<100ms",
    "validation_result": "valid",
    "document_properties": {
      "has_verification_method": true,
      "has_service_endpoint": true,
      "signature_valid": true
    }
  },
  "notes": "Test should be run with warm cache and network connectivity"
}