Initial commit

crates/training/rtx-federated/src/privacy/privacy_budget.rs

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+//! Privacy budget management and accounting
+
+use crate::error::{FederatedError, Result};
+use serde::{Deserialize, Serialize};
+use std::collections::VecDeque;
+use tracing::info;
+
+/// Privacy budget for differential privacy
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PrivacyBudget {
+    pub epsilon: f64,
+    pub delta: f64,
+}
+
+impl PrivacyBudget {
+    pub fn new(epsilon: f64) -> Self {
+        Self {
+            epsilon,
+            delta: 1e-5,
+        }
+    }
+}
+
+/// Privacy accountant for tracking budget consumption
+#[derive(Debug)]
+pub struct PrivacyAccountant {
+    total_budget: PrivacyBudget,
+    consumed_budget: PrivacyBudget,
+    transaction_history: VecDeque<PrivacyTransaction>,
+    max_history_size: usize,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct PrivacyTransaction {
+    pub epsilon_consumed: f64,
+    pub delta_consumed: f64,
+    pub timestamp: chrono::DateTime<chrono::Utc>,
+    pub description: String,
+}
+
+impl PrivacyAccountant {
+    pub fn new(total_budget: PrivacyBudget) -> Self {
+        Self {
+            total_budget,
+            consumed_budget: PrivacyBudget {
+                epsilon: 0.0,
+                delta: 0.0,
+            },
+            transaction_history: VecDeque::new(),
+            max_history_size: 1000,
+        }
+    }
+
+    pub fn consume(&mut self, epsilon: f64, delta: f64, description: String) -> Result<()> {
+        if self.consumed_budget.epsilon + epsilon > self.total_budget.epsilon {
+            return Err(FederatedError::PrivacyBudgetExceeded {
+                remaining: self.total_budget.epsilon - self.consumed_budget.epsilon,
+                requested: epsilon,
+            });
+        }
+
+        self.consumed_budget.epsilon += epsilon;
+        self.consumed_budget.delta += delta;
+
+        let transaction = PrivacyTransaction {
+            epsilon_consumed: epsilon,
+            delta_consumed: delta,
+            timestamp: chrono::Utc::now(),
+            description: description.clone(),
+        };
+
+        self.transaction_history.push_back(transaction);
+
+        if self.transaction_history.len() > self.max_history_size {
+            self.transaction_history.pop_front();
+        }
+
+        info!(
+            "🔒 Privacy budget consumed: ε={:.6}, δ={:.2e} ({})",
+            epsilon, delta, description
+        );
+        Ok(())
+    }
+
+    pub fn remaining_budget(&self) -> PrivacyBudget {
+        PrivacyBudget {
+            epsilon: (self.total_budget.epsilon - self.consumed_budget.epsilon).max(0.0),
+            delta: (self.total_budget.delta - self.consumed_budget.delta).max(0.0),
+        }
+    }
+
+    pub fn budget_utilization(&self) -> f64 {
+        self.consumed_budget.epsilon / self.total_budget.epsilon
+    }
+}