1 files changed, 211 insertions, 0 deletions
diff --git a/timing/src/timerange.rs b/timing/src/timerange.rs
new file mode 100644
index 0000000..8991930
--- /dev/null
+++ b/timing/src/timerange.rs
@@ -0,0 +1,211 @@
+use chrono::{DateTime, Duration, Utc};
+use serde::{Deserialize, Serialize};
+use blake3::Hasher;
+
+/// Represents a fuzzy time range for transaction timestamps
+#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
+pub struct TimeRange {
+    /// Earliest possible timestamp (Unix seconds)
+    pub earliest: i64,
+    /// Latest possible timestamp (Unix seconds)
+    pub latest: i64,
+}
+
+impl TimeRange {
+    /// Minimum allowed range duration (2 hours)
+    pub const MIN_RANGE_SECONDS: i64 = 2 * 3600;
+    /// Maximum allowed range duration (6 hours)
+    pub const MAX_RANGE_SECONDS: i64 = 6 * 3600;
+    /// Maximum age for a transaction (4 hours from latest)
+    pub const MAX_TX_AGE_SECONDS: i64 = 4 * 3600;
+
+    /// Create a new TimeRange around a real timestamp
+    pub fn new(real_time: DateTime<Utc>, range_hours: u32) -> Result<Self, TimeRangeError> {
+        let range_seconds = (range_hours as i64) * 3600;
+
+        if range_seconds < Self::MIN_RANGE_SECONDS {
+            return Err(TimeRangeError::RangeTooSmall);
+        }
+
+        if range_seconds > Self::MAX_RANGE_SECONDS {
+            return Err(TimeRangeError::RangeTooLarge);
+        }
+
+        let half_range = Duration::seconds(range_seconds / 2);
+        let earliest = (real_time - half_range).timestamp();
+        let latest = (real_time + half_range).timestamp();
+
+        Ok(Self { earliest, latest })
+    }
+
+    /// Create a fuzzy range with random padding
+    pub fn new_fuzzy(real_time: DateTime<Utc>) -> Self {
+        use rand::Rng;
+        let mut rng = rand::thread_rng();
+
+        // Random range between 2-6 hours
+        let range_hours = rng.gen_range(2..=6);
+
+        Self::new(real_time, range_hours).expect("Range should be valid")
+    }
+
+    /// Check if this range is valid at current time
+    pub fn is_valid(&self, current_time: DateTime<Utc>) -> bool {
+        let range_duration = self.latest - self.earliest;
+
+        // Check range size
+        if range_duration < Self::MIN_RANGE_SECONDS || range_duration > Self::MAX_RANGE_SECONDS {
+            return false;
+        }
+
+        // Check not too old
+        let age = current_time.timestamp() - self.latest;
+        if age > Self::MAX_TX_AGE_SECONDS {
+            return false;
+        }
+
+        true
+    }
+
+    /// Get the duration of this range in seconds
+    pub fn duration_seconds(&self) -> i64 {
+        self.latest - self.earliest
+    }
+
+    /// Check if a timestamp falls within this range
+    pub fn contains(&self, timestamp: i64) -> bool {
+        timestamp >= self.earliest && timestamp <= self.latest
+    }
+}
+
+/// Zero-knowledge proof that a transaction was created within a time range
+/// Simplified version using hash chains
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct TimeRangeProof {
+    /// Hash at earliest time point
+    pub earliest_hash: [u8; 32],
+    /// Hash at latest time point
+    pub latest_hash: [u8; 32],
+    /// Commitment to the real creation time
+    pub time_commitment: [u8; 32],
+}
+
+impl TimeRangeProof {
+    /// Generate a proof for a real timestamp within a range
+    /// Uses hash chain: H^n(seed) where n = minutes since epoch
+    pub fn generate(
+        seed: &[u8; 32],
+        real_time: DateTime<Utc>,
+        time_range: &TimeRange,
+    ) -> Result<Self, TimeRangeError> {
+        if !time_range.contains(real_time.timestamp()) {
+            return Err(TimeRangeError::TimeOutOfRange);
+        }
+
+        // Convert timestamps to "minutes since epoch" for hash chain
+        let earliest_minutes = time_range.earliest / 60;
+        let latest_minutes = time_range.latest / 60;
+        let real_minutes = real_time.timestamp() / 60;
+
+        // Generate hash chain values
+        let earliest_hash = Self::hash_chain(seed, earliest_minutes as u64);
+        let latest_hash = Self::hash_chain(seed, latest_minutes as u64);
+
+        // Commitment to real time (hash of seed + real_time)
+        let mut hasher = Hasher::new();
+        hasher.update(seed);
+        hasher.update(&real_minutes.to_le_bytes());
+        let time_commitment = *hasher.finalize().as_bytes();
+
+        Ok(Self {
+            earliest_hash,
+            latest_hash,
+            time_commitment,
+        })
+    }
+
+    /// Verify that the proof is internally consistent
+    /// Note: This is a simplified proof system. A production version would use
+    /// proper ZK-SNARKs or Bulletproofs for stronger guarantees
+    pub fn verify(&self, time_range: &TimeRange) -> bool {
+        // In a real implementation, we would verify:
+        // 1. earliest_hash and latest_hash are valid points in hash chain
+        // 2. time_commitment corresponds to a point between them
+        // 3. No information about real_time is leaked
+
+        // For this prototype, we just check the hashes are non-zero
+        self.earliest_hash != [0u8; 32]
+            && self.latest_hash != [0u8; 32]
+            && self.time_commitment != [0u8; 32]
+            && time_range.duration_seconds() > 0
+    }
+
+    /// Hash chain computation: applies blake3 hash n times
+    fn hash_chain(seed: &[u8; 32], iterations: u64) -> [u8; 32] {
+        let mut current = *seed;
+
+        for _ in 0..iterations {
+            let mut hasher = Hasher::new();
+            hasher.update(&current);
+            current = *hasher.finalize().as_bytes();
+        }
+
+        current
+    }
+}
+
+#[derive(Debug, thiserror::Error)]
+pub enum TimeRangeError {
+    #[error("Time range is too small (minimum 2 hours)")]
+    RangeTooSmall,
+
+    #[error("Time range is too large (maximum 6 hours)")]
+    RangeTooLarge,
+
+    #[error("Real timestamp is outside the specified range")]
+    TimeOutOfRange,
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_timerange_creation() {
+        let now = Utc::now();
+        let range = TimeRange::new(now, 4).unwrap();
+
+        assert!(range.duration_seconds() == 4 * 3600);
+        assert!(range.contains(now.timestamp()));
+    }
+
+    #[test]
+    fn test_timerange_validation() {
+        let now = Utc::now();
+        let range = TimeRange::new(now, 4).unwrap();
+
+        assert!(range.is_valid(now));
+        assert!(range.is_valid(now + Duration::hours(1)));
+    }
+
+    #[test]
+    fn test_timerange_proof() {
+        let seed = [42u8; 32];
+        let now = Utc::now();
+        let range = TimeRange::new(now, 4).unwrap();
+
+        let proof = TimeRangeProof::generate(&seed, now, &range).unwrap();
+        assert!(proof.verify(&range));
+    }
+
+    #[test]
+    fn test_fuzzy_range() {
+        let now = Utc::now();
+        let range1 = TimeRange::new_fuzzy(now);
+        let range2 = TimeRange::new_fuzzy(now);
+
+        // Ranges should be valid but potentially different
+        assert!(range1.is_valid(now));
+        assert!(range2.is_valid(now));
+    }
+}