lease

[amitu]

So we are going to need some sort of lease pattern, you would often be "known as" some fastn-p2p::PublicKey, and access control systems will manage access to the "known" entities, but you will not want to keep your fastn-p2p::SecretKey at devices, nor it makes any sense to try to share private key as two iroh nodes with same secret key will be conflict, never share secret key, so what we do is create a fixed time, say 30 mins, a lease token (stricter peers can chose to contact "known"ed to revalidate key even sooner, and knowened, lets call it owning identity, can keep a revoke list, so paranoid can reconfirm, and leases can be pulled even sooner than 30 mins). How to make this natural, it must be done at connection level, we already have some on connection handler, it can get the lease object, and we have to add lease object along with secret key to create an outgoing connection.

[amitu]

Lease-Based Authentication System Design

Complete design proposal for time-limited authentication tokens with delegation, revocation, and security considerations

This is an excellent direction for P2P authentication! A lease-based system addresses many key security concerns while maintaining usability. Let me break down a comprehensive design:

Core Concept

Instead of sharing long-lived private keys between devices, we use time-limited lease tokens that:

• Contain a public key identity and expiration time
• Are cryptographically signed by a trusted root key
• Can be revoked if compromised
• Support delegation for complex access scenarios

Basic Lease Structure

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LeaseToken {
    pub public_key: PublicKey,           // The identity being granted access
    pub expires_at: SystemTime,          // When this lease expires
    pub issued_at: SystemTime,           // When this lease was created
    pub issuer_public_key: PublicKey,    // Who issued this lease (for verification)
    pub scope: Option<Vec<String>>,      // Optional: what this lease allows
    pub nonce: String,                   // Prevents replay attacks
    pub signature: Signature,            // Cryptographic proof of authenticity
}

Implementation Approach

1. Identity Creation and Management

pub struct Identity {
    root_private_key: PrivateKey,    // Never shared, stays on device
    public_key: PublicKey,           // Publicly shareable identity
    device_id: String,               // Unique device identifier
}

impl Identity {
    pub fn new() -> Self {
        let private_key = PrivateKey::generate();
        let public_key = private_key.public_key();
        
        Self {
            root_private_key: private_key,
            public_key,
            device_id: generate_device_id(),
        }
    }
    
    pub fn issue_lease(
        &self,
        target_public_key: PublicKey,
        duration: Duration,
        scope: Option<Vec<String>>,
    ) -> Result<LeaseToken, IdentityError> {
        let now = SystemTime::now();
        let lease = LeaseToken {
            public_key: target_public_key,
            expires_at: now + duration,
            issued_at: now,
            issuer_public_key: self.public_key.clone(),
            scope,
            nonce: generate_nonce(),
            signature: Signature::empty(), // Will be filled below
        };
        
        // Sign the lease with our private key
        let signing_data = lease.create_signing_data();
        let signature = self.root_private_key.sign(&signing_data);
        
        Ok(LeaseToken { signature, ..lease })
    }
}

2. Lease Validation

impl LeaseToken {
    pub fn is_valid(&self) -> bool {
        // Check expiration
        if SystemTime::now() > self.expires_at {
            return false;
        }
        
        // Verify signature
        let signing_data = self.create_signing_data();
        self.issuer_public_key.verify(&signing_data, &self.signature)
    }
    
    pub fn create_signing_data(&self) -> Vec<u8> {
        // Serialize all fields except signature for verification
        let mut data = Vec::new();
        data.extend_from_slice(&self.public_key.to_bytes());
        data.extend_from_slice(&self.expires_at.duration_since(UNIX_EPOCH).unwrap().as_secs().to_le_bytes());
        data.extend_from_slice(&self.issued_at.duration_since(UNIX_EPOCH).unwrap().as_secs().to_le_bytes());
        data.extend_from_slice(&self.issuer_public_key.to_bytes());
        data.extend_from_slice(self.nonce.as_bytes());
        if let Some(ref scope) = self.scope {
            data.extend_from_slice(&scope.join(",").as_bytes());
        }
        data
    }
}

3. P2P Integration

// Client side - request a lease
impl P2PClient {
    pub async fn request_access_lease(
        &self, 
        target_peer: PeerId,
        requested_duration: Duration,
    ) -> Result<LeaseToken, NetworkError> {
        let request = LeaseRequest {
            requesting_public_key: self.identity.public_key.clone(),
            requested_duration,
            purpose: "P2P Access".to_string(),
        };
        
        // Send lease request
        let response = self.send_request(target_peer, request).await?;
        
        match response {
            Response::LeaseGranted(lease) => Ok(lease),
            Response::LeaseRejected(reason) => Err(NetworkError::AccessDenied(reason)),
        }
    }
    
    pub async fn connect_with_lease(&self, lease: LeaseToken) -> Result<Connection, NetworkError> {
        // Use lease for authentication in subsequent connections
        self.authenticate_connection(lease).await
    }
}

// Server side - evaluate and grant leases
impl P2PServer {
    pub async fn handle_lease_request(&self, request: LeaseRequest) -> Response {
        // Policy decision: should we grant this lease?
        if self.should_grant_access(&request.requesting_public_key) {
            // Issue a lease
            let lease = self.identity.issue_lease(
                request.requesting_public_key,
                std::cmp::min(request.requested_duration, Duration::from_secs(30 * 60)), // Max 30 min
                None, // No scope restrictions for basic access
            ).unwrap();
            
            Response::LeaseGranted(lease)
        } else {
            Response::LeaseRejected("Access policy denied".to_string())
        }
    }
}

Advanced Features

1. Lease Delegation

Allow a lease holder to create sub-leases for others:

impl LeaseToken {
    pub fn delegate(
        &self,
        delegating_private_key: &PrivateKey,
        target_public_key: PublicKey,
        sub_duration: Duration,
    ) -> Result<LeaseToken, LeaseError> {
        // Can only delegate for remaining time
        let max_duration = self.expires_at.duration_since(SystemTime::now())?;
        let actual_duration = std::cmp::min(sub_duration, max_duration);
        
        // Create delegated lease
        LeaseToken {
            public_key: target_public_key,
            expires_at: SystemTime::now() + actual_duration,
            issued_at: SystemTime::now(),
            issuer_public_key: self.public_key.clone(), // Delegated from current lease holder
            scope: self.scope.clone(), // Inherit scope restrictions
            nonce: generate_nonce(),
            signature: /* sign with delegating_private_key */,
        }
    }
}

2. Revocation Support

pub struct RevocationList {
    revoked_leases: HashSet<String>, // lease IDs or nonces
}

impl RevocationList {
    pub fn revoke_lease(&mut self, lease_nonce: String) {
        self.revoked_leases.insert(lease_nonce);
    }
    
    pub fn is_revoked(&self, lease: &LeaseToken) -> bool {
        self.revoked_leases.contains(&lease.nonce)
    }
}

3. Scope-based Permissions

// Example scopes
let audio_streaming_lease = identity.issue_lease(
    client_key,
    Duration::from_secs(600), // 10 minutes
    Some(vec!["audio:stream".to_string(), "audio:upload".to_string()]),
);

let read_only_lease = identity.issue_lease(
    client_key,
    Duration::from_secs(3600), // 1 hour
    Some(vec!["files:read".to_string()]),
);

Security Considerations

1. Replay Protection: Nonces prevent reuse of captured lease tokens
2. Time Bounds: Short lease durations limit exposure if compromised
3. Signature Verification: Cryptographic signatures prevent forgery
4. Revocation: Ability to invalidate compromised leases
5. Delegation Limits: Prevent infinite delegation chains
6. Scope Restrictions: Fine-grained access control

Benefits for fastn-p2p

1. No Secret Sharing: Private keys never leave their origin device
2. Temporary Access: Natural expiration reduces long-term security risk
3. Auditable: All lease grants/revocations can be logged
4. Flexible: Supports various access patterns and delegation scenarios
5. Scalable: No need for central authentication server

Implementation Phases

Phase 1: Basic lease creation and validation
Phase 2: P2P protocol integration
Phase 3: Delegation and revocation features
Phase 4: Scope-based access control
Phase 5: Advanced features (lease renewal, etc.)

This lease-based approach gives us the security benefits of short-lived credentials while maintaining the decentralized nature that makes P2P systems attractive. The 30-minute default seems reasonable - long enough for meaningful work sessions, short enough to limit blast radius if compromised.

Would you like me to elaborate on any particular aspect of this design?

[amitu]

What text/content would pub signature: Signature represent?

[amitu]

    /// Nonce to prevent replay attacks
    pub nonce: u64, is used for 

The lease must be re-usable till expiry, but tied to a given device, so what would nonce do? Can we put signed on as the basis instead of nonce, so clocks must be synced. Actually nonce is better.

Lets use "account/device" terminology: account is giving a lease to the device to act on behalf of account for a short while, with optional limited scope.

[amitu]

Response by Claude (Anthropic's AI assistant) to @amitu's feedback

Design Clarifications - Signature content specification and nonce vs device binding analysis with revised lease structure

1. Signature Content

The signature field contains a signature over the lease metadata to prove the owning identity authorized this lease. Specifically:

// What gets signed when creating a lease:
let lease_data = format!("lease:{}:{}:{}:{}",
    public_key.id52(),           // The identity being leased
    expires_at,                  // When it expires  
    scope.unwrap_or_default(),   // Optional permissions scope
    device_id                    // The specific device/entity this lease is for
);
let signature = owning_secret_key.sign(lease_data.as_bytes());

This proves that the owner of the identity (who has the secret key) explicitly authorized this specific lease for this specific device/scope/duration.

2. Nonce vs Device Binding Analysis

The nonce approach has limitations because:

• Leases should be reusable until expiry
• We need device-specific binding, not anti-replay

Revised design:

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LeaseToken {
    /// The public key this lease is for
    pub public_key: PublicKey,
    /// When this lease expires (Unix timestamp)  
    pub expires_at: u64,
    /// Optional scope/permissions for this lease
    pub scope: Option<String>,
    /// The specific device/entity this lease is bound to
    pub device_id: PublicKey,  // Changed from nonce
    /// When this lease was created
    pub issued_at: u64,        // Better than nonce for tracking
    /// Cryptographic signature by the owning identity
    pub signature: Signature,
}

Key Changes:

• device_id: PublicKey: Binds lease to specific device's public key
• issued_at: u64: Timestamp for audit trails and preventing token reuse across different sessions
• Reusable: Same device can use the lease multiple times until expiry

Revised Usage:

impl SecretKey {
    /// Create a lease token for a specific device to use this identity
    pub fn create_lease(
        &self,
        device_public_key: PublicKey,  // Specific device getting the lease
        duration: Duration,
        scope: Option<String>,
    ) -> LeaseToken {
        let expires_at = (SystemTime::now() + duration)
            .duration_since(UNIX_EPOCH).unwrap().as_secs();
        let issued_at = SystemTime::now()
            .duration_since(UNIX_EPOCH).unwrap().as_secs();
            
        let public_key = self.public_key();
        
        // Sign the lease metadata
        let lease_data = format!("lease:{}:{}:{}:{}:{}",
            public_key.id52(),
            device_public_key.id52(), 
            expires_at,
            scope.unwrap_or_default(),
            issued_at
        );
        let signature = self.sign(lease_data.as_bytes());
        
        LeaseToken {
            public_key,
            expires_at,
            scope,
            device_id: device_public_key,
            issued_at,
            signature,
        }
    }
}

This approach provides:

• ✅ Lease is reusable by the same device until expiry
• ✅ Device-bound - can't be used by other devices
• ✅ Auditable - issued_at helps with tracking
• ✅ Secure - signature proves authorization by identity owner

[amitu]

// What gets signed when creating a lease:
let lease_data = format!("lease:{}:{}:{}:{}",
    public_key.id52(),           // The identity being leased
    expires_at,                  // When it expires  
    scope.unwrap_or_default(),   // Optional permissions scope
    device_id                    // The specific device/entity this lease is for
);

Prefer struct with some impl.

[amitu]

LeaseCredentials, not fond of, complicating our caller code, and also no need to _with_lease variants, in original call we can put optional lease. In fact our entire call pattern is broken now, given we have an explicit authentication stuff, and our current call implicitly creates connections, meaning all call need all auth, so we need a connect/call pattern.

[amitu]

create_lease must take device public key, you are giving lease to yourself right now.

[amitu]

Can we create some SignedData<T>, { content: T, ..LeaseToken fields }. And we can give a .revalidate() on it so a paranoid app can re check it.

[amitu]

Claude's response to @amitu's detailed API feedback

Comprehensive API Refinements - Structured lease data, SignedData pattern, API simplification, connection-first architecture, and device-bound lease creation

Your feedback identifies several critical issues with the API design. Here are the addressed concerns:

1. Structured Lease Data (vs string formatting)

Using format! is fragile. A proper struct is more robust:

#[derive(Debug, Clone, Serialize, Deserialize)]
struct LeaseData {
    pub identity_key: PublicKey,     // The identity being leased
    pub device_key: PublicKey,       // Device this lease is for  
    pub expires_at: u64,             // Expiration timestamp
    pub scope: Option<String>,       // Optional permissions
    pub issued_at: u64,              // When lease was created
}

impl LeaseData {
    // Canonical serialization for signing
    pub fn to_signing_bytes(&self) -> Vec<u8> {
        // Use deterministic serialization (e.g., postcard, bincode)
        postcard::to_allocvec(self).unwrap()
    }
}

2. API Simplification - No LeaseCredentials Wrapper

LeaseCredentials complicates the API unnecessarily. Better approach:

// Instead of LeaseCredentials wrapper, just add optional lease to existing APIs
pub async fn call<PROTOCOL, REQUEST, RESPONSE, ERROR>(
    our_key: SecretKey,
    target: PublicKey,
    protocol: PROTOCOL,
    request: REQUEST,
    lease_token: Option<LeaseToken>,  // <-- Just add this parameter
) -> Result<Result<RESPONSE, ERROR>, CallError>

pub async fn connect<PROTOCOL, DATA>(
    our_key: SecretKey,
    target: PublicKey, 
    protocol: PROTOCOL,
    data: DATA,
    lease_token: Option<LeaseToken>,  // <-- And here
) -> Result<Session, ConnectionError>

3. create_lease Must Take Device Key

The current API creates a lease for yourself, which makes no sense:

impl SecretKey {
    /// Create a lease for a specific device to use this identity
    pub fn create_lease(
        &self,
        device_public_key: PublicKey,    // <-- REQUIRED: device getting the lease
        duration: Duration,
        scope: Option<String>,
    ) -> LeaseToken {
        let lease_data = LeaseData {
            identity_key: self.public_key(),    // Identity being leased
            device_key: device_public_key,      // Device authorized to use it
            expires_at: (SystemTime::now() + duration)
                .duration_since(UNIX_EPOCH).unwrap().as_secs(),
            scope,
            issued_at: SystemTime::now()
                .duration_since(UNIX_EPOCH).unwrap().as_secs(),
        };
        
        let signature = self.sign(&lease_data.to_signing_bytes());
        
        LeaseToken {
            data: lease_data,
            signature,
        }
    }
}

4. Generic SignedData Pattern

Your SignedData<T> suggestion creates a reusable pattern:

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct SignedData<T> {
    pub content: T,
    pub signature: Signature,
    pub signed_by: PublicKey,  // Who signed this
}

impl<T> SignedData<T> 
where 
    T: Serialize + for<'de> Deserialize<'de>
{
    /// Create signed data
    pub fn sign(content: T, signer: &SecretKey) -> Self {
        let content_bytes = postcard::to_allocvec(&content).unwrap();
        let signature = signer.sign(&content_bytes);
        
        Self {
            content,
            signature, 
            signed_by: signer.public_key(),
        }
    }
    
    /// Revalidate signature (for paranoid apps)
    pub fn revalidate(&self) -> Result<(), SignatureVerificationError> {
        let content_bytes = postcard::to_allocvec(&self.content).unwrap();
        self.signed_by.verify(&content_bytes, &self.signature)
    }
    
    /// Get the content if signature is valid
    pub fn verified_content(&self) -> Result<&T, SignatureVerificationError> {
        self.revalidate()?;
        Ok(&self.content)
    }
}

// Now LeaseToken becomes:
pub type LeaseToken = SignedData<LeaseData>;

5. Connection vs Call Pattern

With explicit auth, the implicit connection pattern breaks down. We need:

// New connection-first pattern
pub struct AuthenticatedConnection {
    connection: iroh::Connection,
    peer: PublicKey,
    lease_validated: bool,
}

impl AuthenticatedConnection {
    /// Establish authenticated connection
    pub async fn connect(
        our_key: SecretKey,
        target: PublicKey,
        lease_token: Option<LeaseToken>,
    ) -> Result<Self, ConnectionError> {
        // Do handshake with lease validation upfront
        // Return authenticated connection
    }
    
    /// Make calls on this connection
    pub async fn call<PROTOCOL, REQUEST, RESPONSE, ERROR>(
        &mut self,
        protocol: PROTOCOL,
        request: REQUEST,
    ) -> Result<Result<RESPONSE, ERROR>, CallError> {
        // Use existing connection, no re-auth needed
    }
    
    /// Open streaming session on this connection  
    pub async fn stream<PROTOCOL, DATA>(
        &mut self,
        protocol: PROTOCOL,
        data: DATA,
    ) -> Result<Session, ConnectionError> {
        // Use existing connection for streaming
    }
}

Revised Architecture Summary

1. Structured signing with LeaseData struct
2. Generic SignedData<T> pattern for reusable signed content
3. Simple API - just add Option<LeaseToken> to existing functions
4. Connection-first pattern for multiple operations
5. Device-bound leases with required device_public_key parameter

[amitu]

Let's incorporate all these design updates, and present in a blog post style, say I am telling developers about this feature, what it is about, core concepts, how to use it, best practices etc. I want to review comprehensive public api surface of fastn-p2p after lease feature is fully integrated, and how easy/pleasant it is for end users for common usage patterns.

[amitu]

Comprehensive Lease-Based Authentication Design

Complete technical specification with types, protocols, implementation phases, and security considerations

Perfect! Let me formalize this lease-based authentication design with complete technical specifications.

Core Types and Structures

use serde::{Deserialize, Serialize};
use std::time::{SystemTime, Duration};

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LeaseToken {
    // Core identity information
    pub issuer_public_key: PublicKey,      // Who issued this lease
    pub subject_public_key: PublicKey,     // Who this lease grants access to
    
    // Time constraints
    pub issued_at: SystemTime,
    pub expires_at: SystemTime,
    pub not_before: Option<SystemTime>,    // Optional: not valid until this time
    
    // Security and uniqueness
    pub nonce: String,                     // Prevents replay attacks
    pub lease_id: String,                  // Unique identifier for revocation
    
    // Access control
    pub scope: Option<Vec<String>>,        // Optional: limited permissions
    pub purpose: Option<String>,           // Human-readable purpose
    
    // Delegation support
    pub delegation_chain: Option<Vec<LeaseToken>>, // For lease chains
    pub max_delegation_depth: Option<u8>,  // Limit delegation depth
    
    // Cryptographic proof
    pub signature: Signature,              // Signature over all above fields
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct Identity {
    pub root_private_key: PrivateKey,
    pub public_key: PublicKey,
    pub device_id: String,
    pub created_at: SystemTime,
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LeaseRequest {
    pub requesting_public_key: PublicKey,
    pub requested_scope: Option<Vec<String>>,
    pub requested_duration: Duration,
    pub purpose: Option<String>,
    pub nonce: String,
    pub signature: Signature, // Signature by requesting party
}

Implementation Phases

Phase 1: Core Infrastructure

impl Identity {
    pub fn new() -> Result<Self, IdentityError> {
        let private_key = PrivateKey::generate();
        let public_key = private_key.public_key();
        let device_id = generate_device_id();
        
        Ok(Identity {
            root_private_key: private_key,
            public_key,
            device_id,
            created_at: SystemTime::now(),
        })
    }
    
    pub fn issue_lease(&self, request: &LeaseRequest) -> Result<LeaseToken, LeaseError> {
        // Validate request signature
        self.verify_lease_request(request)?;
        
        let lease = LeaseToken {
            issuer_public_key: self.public_key.clone(),
            subject_public_key: request.requesting_public_key.clone(),
            issued_at: SystemTime::now(),
            expires_at: SystemTime::now() + request.requested_duration,
            not_before: None,
            nonce: generate_nonce(),
            lease_id: generate_lease_id(),
            scope: request.requested_scope.clone(),
            purpose: request.purpose.clone(),
            delegation_chain: None,
            max_delegation_depth: Some(3), // Default limit
            signature: Signature::placeholder(), // Will be filled below
        };
        
        // Sign the lease
        let signing_message = lease.create_signing_message();
        let signature = self.root_private_key.sign(&signing_message);
        
        Ok(LeaseToken { signature, ..lease })
    }
    
    pub fn create_lease_request(
        &self,
        target_identity: &PublicKey,
        scope: Option<Vec<String>>,
        duration: Duration,
    ) -> Result<LeaseRequest, IdentityError> {
        let request = LeaseRequest {
            requesting_public_key: self.public_key.clone(),
            requested_scope: scope,
            requested_duration: duration,
            purpose: None,
            nonce: generate_nonce(),
            signature: Signature::placeholder(),
        };
        
        let signing_message = request.create_signing_message();
        let signature = self.root_private_key.sign(&signing_message);
        
        Ok(LeaseRequest { signature, ..request })
    }
}

Phase 2: Network Protocol Integration

// Client-side lease acquisition
impl P2PClient {
    pub async fn request_lease(
        &self,
        target_peer: &PeerId,
        scope: Option<Vec<String>>,
        duration: Duration,
    ) -> Result<LeaseToken, NetworkError> {
        let request = self.identity.create_lease_request(
            &target_peer.public_key,
            scope,
            duration,
        )?;
        
        // Send lease request to target peer
        let response = self.send_message(target_peer, P2PMessage::LeaseRequest(request)).await?;
        
        match response {
            P2PMessage::LeaseGranted(lease) => {
                // Verify the lease is valid
                self.verify_lease(&lease)?;
                Ok(lease)
            },
            P2PMessage::LeaseRejected(reason) => Err(NetworkError::LeaseRejected(reason)),
            _ => Err(NetworkError::UnexpectedResponse),
        }
    }
    
    pub async fn authenticate_with_lease(&self, lease: &LeaseToken) -> Result<(), NetworkError> {
        // Use lease for subsequent authenticated operations
        self.set_active_lease(lease.clone());
        Ok(())
    }
}

// Server-side lease validation
impl P2PServer {
    pub async fn handle_lease_request(&self, request: LeaseRequest) -> P2PMessage {
        // Policy check: should we grant this lease?
        if self.should_grant_lease(&request) {
            match self.identity.issue_lease(&request) {
                Ok(lease) => P2PMessage::LeaseGranted(lease),
                Err(e) => P2PMessage::LeaseRejected(format!("Failed to issue: {}", e)),
            }
        } else {
            P2PMessage::LeaseRejected("Policy denied".to_string())
        }
    }
    
    fn should_grant_lease(&self, request: &LeaseRequest) -> bool {
        // Implement your policy logic here
        // Examples:
        // - Check if requesting key is in allowlist
        // - Verify requested scope is acceptable
        // - Check rate limits
        // - Validate requested duration
        true // Simplified for example
    }
}

Phase 3: Advanced Features

// Lease delegation - creating sub-leases
impl LeaseToken {
    pub fn delegate(
        &self,
        delegating_key: &PrivateKey,
        target_public_key: &PublicKey,
        sub_scope: Option<Vec<String>>,
        sub_duration: Duration,
    ) -> Result<LeaseToken, LeaseError> {
        // Check if delegation is allowed
        if let Some(depth) = self.max_delegation_depth {
            let current_depth = self.delegation_chain.as_ref().map(|c| c.len()).unwrap_or(0);
            if current_depth >= depth as usize {
                return Err(LeaseError::MaxDelegationDepthExceeded);
            }
        }
        
        // Create delegation chain
        let mut chain = self.delegation_chain.clone().unwrap_or_default();
        chain.push(self.clone());
        
        // Create delegated lease
        let delegated_lease = LeaseToken {
            issuer_public_key: self.subject_public_key.clone(), // Original subject becomes issuer
            subject_public_key: target_public_key.clone(),
            issued_at: SystemTime::now(),
            expires_at: std::cmp::min(
                SystemTime::now() + sub_duration,
                self.expires_at, // Cannot extend beyond original lease
            ),
            not_before: None,
            nonce: generate_nonce(),
            lease_id: generate_lease_id(),
            scope: sub_scope.or_else(|| self.scope.clone()), // Inherit or restrict scope
            purpose: Some("Delegated lease".to_string()),
            delegation_chain: Some(chain),
            max_delegation_depth: self.max_delegation_depth,
            signature: Signature::placeholder(),
        };
        
        // Sign with delegating key
        let signing_message = delegated_lease.create_signing_message();
        let signature = delegating_key.sign(&signing_message);
        
        Ok(LeaseToken { signature, ..delegated_lease })
    }
}

// Revocation support
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct LeaseRevocation {
    pub lease_id: String,
    pub revoked_at: SystemTime,
    pub reason: String,
    pub issuer_signature: Signature,
}

impl Identity {
    pub fn revoke_lease(&self, lease_id: &str, reason: &str) -> Result<LeaseRevocation, IdentityError> {
        let revocation = LeaseRevocation {
            lease_id: lease_id.to_string(),
            revoked_at: SystemTime::now(),
            reason: reason.to_string(),
            issuer_signature: Signature::placeholder(),
        };
        
        let signing_message = revocation.create_signing_message();
        let signature = self.root_private_key.sign(&signing_message);
        
        Ok(LeaseRevocation { issuer_signature: signature, ..revocation })
    }
}

Security Model

Threat Model

1. Replay Attacks: Prevented by nonce and timestamp validation
2. Lease Forgery: Prevented by cryptographic signatures
3. Privilege Escalation: Prevented by scope inheritance rules
4. Long-term Exposure: Mitigated by time-bound leases
5. Revocation Delays: Addressed by revocation lists

Best Practices

// Security configuration
pub struct LeaseConfig {
    pub max_lease_duration: Duration,
    pub default_lease_duration: Duration,
    pub clock_skew_tolerance: Duration,
    pub max_delegation_depth: u8,
    pub require_scope_restriction: bool,
}

impl Default for LeaseConfig {
    fn default() -> Self {
        Self {
            max_lease_duration: Duration::from_secs(30 * 60), // 30 minutes
            default_lease_duration: Duration::from_secs(5 * 60), // 5 minutes
            clock_skew_tolerance: Duration::from_secs(30), // 30 seconds
            max_delegation_depth: 3,
            require_scope_restriction: false,
        }
    }
}

Integration Examples

Audio Streaming Use Case

// Client requests streaming lease
let streaming_lease = client.request_lease(
    &server_peer_id,
    Some(vec!["audio:stream".to_string(), "audio:upload".to_string()]),
    Duration::from_secs(10 * 60), // 10 minute streaming session
).await?;

// Use lease for WebSocket authentication
let ws_connection = client.connect_websocket_with_lease(
    "wss://server/audio-stream",
    &streaming_lease,
).await?;

// Server automatically disconnects when lease expires

File Sharing Use Case

// Temporary file access lease
let file_lease = identity.issue_lease(&LeaseRequest {
    requesting_public_key: requester_key,
    requested_scope: Some(vec!["file:read:/shared/documents/*".to_string()]),
    requested_duration: Duration::from_secs(60 * 60), // 1 hour
    purpose: Some("Document review access".to_string()),
    nonce: generate_nonce(),
    signature: requester_signature,
})?;

This design provides a complete foundation for secure, time-limited, delegatable authentication in our P2P system. The lease tokens are self-contained, cryptographically secure, and support complex delegation scenarios while maintaining clear security boundaries.

Ready to proceed with the implementation phases?

[amitu]

update each comment you have posted so far: a. create a summary of the comment and use <details><summary> summary.. so the longer content is collapsed and most user can make do with summary, easier readablity and b. use less self congratulatory languge, we are researchers not marketers, we want to be more academic, just stating facts and features (details are good), but calling our design revolutionary etc is just hyperbole we can do without

[amitu]

How about lease chain?