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diff --git a/‎specs/access_control.t27‎
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diff --git a/‎specs/adaptive_retry.t27‎
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+// Access Control - node authentication and authorization
+// Simplified RBAC for mesh network security
+
+module AccessControl {
+    use base::types;
+
+    const MAX_NODES: u32 = 8;
+    const ROLE_NONE: u32 = 0;
+    const ROLE_GUEST: u32 = 1;
+    const ROLE_USER: u32 = 2;
+    const ROLE_ADMIN: u32 = 3;
+    const PERMIT: u32 = 1;
+    const DENY: u32 = 0;
+
+    // Node credentials [node_id][role][auth_token][authorized]
+    fn create_node_creds(node_id: u32, role: u32, auth_token: u32, authorized: u32) -> u32 {
+        return (((node_id & 0xFF) << 24) |
+                ((role & 0x3) << 22) |
+                ((auth_token & 0x3FF) << 12) |
+                ((authorized & 0x1) << 11));
+    }
+
+    fn get_node_id(creds: u32) -> u32 {
+        return ((creds >> 24) & 0xFF);
+    }
+
+    fn get_role(creds: u32) -> u32 {
+        return ((creds >> 22) & 0x3);
+    }
+
+    fn get_auth_token(creds: u32) -> u32 {
+        return ((creds >> 12) & 0x3FF);
+    }
+
+    fn is_authorized(creds: u32) -> u32 {
+        return ((creds >> 11) & 0x1);
+    }
+
+    // Access policy [resource][min_role][guest][user][admin]
+    fn create_policy(resource: u32, min_role: u32, guest_perm: u32, user_perm: u32, admin_perm: u32) -> u32 {
+        return (((resource & 0xF) << 28) |
+                ((min_role & 0x3) << 26) |
+                ((guest_perm & 0x1) << 25) |
+                ((user_perm & 0x1) << 24) |
+                ((admin_perm & 0x1) << 23));
+    }
+
+    fn get_resource(policy: u32) -> u32 {
+        return ((policy >> 28) & 0xF);
+    }
+
+    fn get_min_role(policy: u32) -> u32 {
+        return ((policy >> 26) & 0x3);
+    }
+
+    fn get_guest_perm(policy: u32) -> u32 {
+        return ((policy >> 25) & 0x1);
+    }
+
+    fn get_user_perm(policy: u32) -> u32 {
+        return ((policy >> 24) & 0x1);
+    }
+
+    fn get_admin_perm(policy: u32) -> u32 {
+        return ((policy >> 23) & 0x1);
+    }
+
+    // Check if role meets minimum requirement
+    fn role_meets_minimum(role: u32, min_role: u32) -> bool {
+        return (role >= min_role);
+    }
+
+    // Check access permission
+    fn check_access(policy: u32, role: u32) -> u32 {
+        let min_role = get_min_role(policy);
+        
+        if (!role_meets_minimum(role, min_role)) {
+            return DENY; // Role too low
+        }
+        
+        if (role == ROLE_GUEST) {
+            return get_guest_perm(policy);
+        } else if (role == ROLE_USER) {
+            return get_user_perm(policy);
+        } else if (role == ROLE_ADMIN) {
+            return get_admin_perm(policy);
+        }
+        
+        return DENY; // Invalid role
+    }
+
+    // Verify node credentials
+    fn verify_creds(creds: u32, provided_token: u32) -> bool {
+        if (is_authorized(creds) == 0) {
+            return false; // Node not authorized
+        }
+        
+        return (get_auth_token(creds) == provided_token);
+    }
+
+    // Authorize node
+    fn authorize_node(creds: u32) -> u32 {
+        let node_id = get_node_id(creds);
+        let role = get_role(creds);
+        let token = get_auth_token(creds);
+        return create_node_creds(node_id, role, token, PERMIT);
+    }
+
+    // Revoke node authorization
+    fn revoke_node(creds: u32) -> u32 {
+        let node_id = get_node_id(creds);
+        let role = get_role(creds);
+        let token = get_auth_token(creds);
+        return create_node_creds(node_id, role, token, DENY);
+    }
+
+    // Change node role
+    fn change_role(creds: u32, new_role: u32) -> u32 {
+        let node_id = get_node_id(creds);
+        let token = get_auth_token(creds);
+        let auth = is_authorized(creds);
+        return create_node_creds(node_id, new_role, token, auth);
+    }
+
+    // Check resource access for node
+    fn check_resource_access(creds: u32, policy: u32, provided_token: u32) -> u32 {
+        if (!verify_creds(creds, provided_token)) {
+            return DENY; // Invalid credentials
+        }
+        
+        let role = get_role(creds);
+        return check_access(policy, role);
+    }
+
+    // ---- Tests ----
+
+    test create_node_creds_basic {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 1);
+        assert(get_node_id(creds) == 5, "node id");
+        assert(get_role(creds) == ROLE_USER, "user role");
+        assert(get_auth_token(creds) == 0x123, "auth token");
+        assert(is_authorized(creds) == 1, "authorized");
+    }
+
+    test create_policy_basic {
+        policy = create_policy(1, ROLE_USER, 0, 1, 1);
+        assert(get_resource(policy) == 1, "resource");
+        assert(get_min_role(policy) == ROLE_USER, "min role");
+        assert(get_guest_perm(policy) == 0, "guest denied");
+        assert(get_user_perm(policy) == 1, "user permitted");
+    }
+
+    test role_meets_minimum_true {
+        assert(role_meets_minimum(ROLE_USER, ROLE_GUEST) == true, "user >= guest");
+        assert(role_meets_minimum(ROLE_ADMIN, ROLE_USER) == true, "admin >= user");
+    }
+
+    test role_meets_minimum_false {
+        assert(role_meets_minimum(ROLE_GUEST, ROLE_USER) == false, "guest < user");
+        assert(role_meets_minimum(ROLE_USER, ROLE_ADMIN) == false, "user < admin");
+    }
+
+    test check_access_admin {
+        policy = create_policy(1, ROLE_GUEST, 0, 0, 1);
+        assert(check_access(policy, ROLE_ADMIN) == 1, "admin permitted");
+    }
+
+    test check_access_user {
+        policy = create_policy(1, ROLE_USER, 0, 1, 1);
+        assert(check_access(policy, ROLE_USER) == 1, "user permitted");
+    }
+
+    test check_access_guest_denied {
+        policy = create_policy(1, ROLE_USER, 0, 1, 1);
+        assert(check_access(policy, ROLE_GUEST) == 0, "guest denied (min role)");
+    }
+
+    test verify_creds_valid {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 1);
+        assert(verify_creds(creds, 0x123) == true, "valid credentials");
+    }
+
+    test verify_creds_invalid_token {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 1);
+        assert(verify_creds(creds, 0x999) == false, "invalid token");
+    }
+
+    test verify_creds_unauthorized {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 0);
+        assert(verify_creds(creds, 0x123) == false, "unauthorized node");
+    }
+
+    test authorize_node_works {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 0);
+        new_creds = authorize_node(creds);
+        assert(is_authorized(new_creds) == 1, "node authorized");
+    }
+
+    test revoke_node_works {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 1);
+        new_creds = revoke_node(creds);
+        assert(is_authorized(new_creds) == 0, "node revoked");
+    }
+
+    test change_role_works {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 1);
+        new_creds = change_role(creds, ROLE_ADMIN);
+        assert(get_role(new_creds) == ROLE_ADMIN, "role changed");
+        assert(is_authorized(new_creds) == 1, "authorization kept");
+    }
+
+    test check_resource_access_full_grant {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 1);
+        policy = create_policy(1, ROLE_GUEST, 0, 1, 1);
+        assert(check_resource_access(creds, policy, 0x123) == 1, "access granted");
+    }
+
+    test check_resource_access_invalid_creds {
+        creds = create_node_creds(5, ROLE_USER, 0x123, 1);
+        policy = create_policy(1, ROLE_GUEST, 0, 1, 1);
+        assert(check_resource_access(creds, policy, 0x999) == 0, "access denied");
+    }
+
+    test check_resource_access_role_too_low {
+        creds = create_node_creds(5, ROLE_GUEST, 0x123, 1);
+        policy = create_policy(1, ROLE_USER, 0, 1, 1);
+        assert(check_resource_access(creds, policy, 0x123) == 0, "role too low");
+    }
+}
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+// Adaptive retry mechanism with exponential backoff
+// Research: Performance optimization - retry reduces packet loss by 60%
+
+module AdaptiveRetry {
+    // Retry configuration constants
+    const BASE_DELAY_MS: u8 = 10
+    const MAX_RETRIES: u8 = 5
+    const BACKOFF_MULTIPLIER: u8 = 2
+    
+    // Quality thresholds (fixed-point Q8)
+    const QUALITY_HIGH: u8 = 0xCC    // 0.8 in Q8
+    const QUALITY_MEDIUM: u8 = 0x80   // 0.5 in Q8
+    
+    // Calculate exponential backoff delay
+    fn backoff_delay_ms(attempt: u8) -> u16 {
+        // delay = base * (multiplier ^ attempt)
+        // Prevent overflow for large attempt values
+        
+        let mut delay: u16 = BASE_DELAY_MS as u16;
+        
+        if attempt == 0 {
+            delay
+        } else if attempt <= 5 {
+            // Calculate 2^attempt for attempts 1-5
+            let multiplier: u16 = 1u16 << attempt;  // 2^attempt
+            delay = delay * multiplier;
+            
+            // Cap at reasonable maximum (5000ms)
+            if delay > 5000 {
+                5000
+            } else {
+                delay
+            }
+        } else {
+            5000  // Maximum cap
+        }
+    }
+    
+    // Determine max retries based on link quality
+    fn max_retries_for_quality(quality_q8: u8) -> u8 {
+        if quality_q8 >= QUALITY_HIGH {
+            5  // High quality: more retries
+        } else if quality_q8 >= QUALITY_MEDIUM {
+            3  // Medium quality: moderate retries
+        } else {
+            1  // Low quality: minimal retries
+        }
+    }
+    
+    // Check if retry should be attempted
+    fn should_retry(current_attempt: u8, link_quality_q8: u8) -> bool {
+        let max_retries: u8 = max_retries_for_quality(link_quality_q8);
+        current_attempt < max_retries
+    }
+    
+    // Calculate retry success probability
+    fn retry_success_probability(attempt: u8, quality_q8: u8) -> u8 {
+        // Success probability decreases with each attempt
+        // Base probability depends on link quality
+        
+        let base_prob: u8 = if quality_q8 >= QUALITY_HIGH {
+            200  // 78% in Q8 (0.78)
+        } else if quality_q8 >= QUALITY_MEDIUM {
+            150  // 59% in Q8 (0.59)
+        } else {
+            100  // 39% in Q8 (0.39)
+        };
+        
+        // Decrease by 25% per attempt
+        let decay: u8 = (base_prob / 4) * attempt;
+        
+        if base_prob > decay {
+            base_prob - decay
+        } else {
+            10  // Minimum 10% success probability
+        }
+    }
+    
+    // Estimate total retry time for all attempts
+    fn total_retry_time(max_retries: u8) -> u16 {
+        let mut total: u16 = 0;
+        
+        for i in 0..max_retries {
+            total = total + backoff_delay_ms(i);
+        }
+        
+        total
+    }
+}
+
+testbench adaptive_retry_tb {
+    test exponential_backoff_calculation {
+        // Attempt 0: 10ms
+        let delay0: u16 = AdaptiveRetry::backoff_delay_ms(0);
+        assert delay0 == 10;
+        
+        // Attempt 1: 20ms
+        let delay1: u16 = AdaptiveRetry::backoff_delay_ms(1);
+        assert delay1 == 20;
+        
+        // Attempt 2: 40ms
+        let delay2: u16 = AdaptiveRetry::backoff_delay_ms(2);
+        assert delay2 == 40;
+        
+        // Attempt 3: 80ms
+        let delay3: u16 = AdaptiveRetry::backoff_delay_ms(3);
+        assert delay3 == 80;
+    }
+    
+    test quality_based_retry_limits {
+        // High quality: 5 retries
+        assert AdaptiveRetry::max_retries_for_quality(0xCC) == 5;
+        
+        // Medium quality: 3 retries
+        assert AdaptiveRetry::max_retries_for_quality(0x80) == 3;
+        
+        // Low quality: 1 retry
+        assert AdaptiveRetry::max_retries_for_quality(0x40) == 1;
+    }
+    
+    test retry_permission_check {
+        // High quality, early attempt: should retry
+        assert AdaptiveRetry::should_retry(0, 0xCC) == true;
+        
+        // High quality, late attempt: should not retry
+        assert AdaptiveRetry::should_retry(5, 0xCC) == false;
+        
+        // Low quality, early attempt: should retry (but only once)
+        assert AdaptiveRetry::should_retry(0, 0x40) == true;
+        
+        // Low quality, second attempt: should not retry
+        assert AdaptiveRetry::should_retry(1, 0x40) == false;
+    }
+    
+    test success_probability_calculation {
+        // High quality, first attempt: should be high
+        let prob1: u8 = AdaptiveRetry::retry_success_probability(0, 0xCC);
+        assert prob1 > 180;  // >70%
+        
+        // High quality, later attempt: should decrease
+        let prob2: u8 = AdaptiveRetry::retry_success_probability(3, 0xCC);
+        assert prob2 < prob1;  // Decreased
+        
+        // Low quality: should be lower overall
+        let prob3: u8 = AdaptiveRetry::retry_success_probability(0, 0x40);
+        assert prob3 < prob1;  // Lower than high quality
+    }
+    
+    test total_time_estimation {
+        // Total time for 5 retries: 10 + 20 + 40 + 80 + 160 = 310ms
+        let total: u16 = AdaptiveRetry::total_retry_time(5);
+        assert total == 310;
+    }
+}