Rename end_hash to id

README.md

@@ -71,9 +71,9 @@ fn main() {
 Running the program should produce a log similar to:
 
 ```rust
-Entry { num_hashes: 0, end_hash: [0, ...], event: Tick }
-Entry { num_hashes: 2, end_hash: [67, ...], event: Transaction { data: [37, ...] } }
-Entry { num_hashes: 3, end_hash: [123, ...], event: Tick }
+Entry { num_hashes: 0, id: [0, ...], event: Tick }
+Entry { num_hashes: 2, id: [67, ...], event: Transaction { data: [37, ...] } }
+Entry { num_hashes: 3, id: [123, ...], event: Tick }
 ```
 
 Proof-of-History
@@ -86,7 +86,7 @@ assert!(verify_slice(&entries, &seed));
 ```
 
 [It's a proof!](https://en.wikipedia.org/wiki/Curry–Howard_correspondence) For each entry returned by the
-historian, we can verify that `end_hash` is the result of applying a sha256 hash to the previous `end_hash`
+historian, we can verify that `id` is the result of applying a sha256 hash to the previous `id`
 exactly `num_hashes` times, and then hashing then event data on top of that. Because the event data is
 included in the hash, the events cannot be reordered without regenerating all the hashes.
 

diagrams/historian.msc

@@ -1,17 +1,17 @@
 msc {
   client,historian,logger;
 
-  logger=>historian [ label = "e0 = Entry{hash: h0, n: 0, event: Tick}" ] ;
+  logger=>historian [ label = "e0 = Entry{id: h0, n: 0, event: Tick}" ] ;
   logger=>logger [ label = "h1 = hash(h0)" ] ;
   logger=>logger [ label = "h2 = hash(h1)" ] ;
   client=>historian [ label = "Claim(d0)" ] ;
   historian=>logger [ label = "Claim(d0)" ] ;
   logger=>logger [ label = "h3 = hash(h2 + d0)" ] ;
-  logger=>historian [ label = "e1 = Entry{hash: hash(h3), n: 2, event: Claim(d0)}" ] ;
+  logger=>historian [ label = "e1 = Entry{id: hash(h3), n: 2, event: Claim(d0)}" ] ;
   logger=>logger [ label = "h4 = hash(h3)" ] ;
   logger=>logger [ label = "h5 = hash(h4)" ] ;
   logger=>logger [ label = "h6 = hash(h5)" ] ;
-  logger=>historian [ label = "e2 = Entry{hash: h6, n: 3, event: Tick}" ] ;
+  logger=>historian [ label = "e2 = Entry{id: h6, n: 3, event: Tick}" ] ;
   client=>historian [ label = "collect()" ] ;
   historian=>client [ label = "entries = [e0, e1, e2]" ] ;
   client=>client [ label = "verify_slice(entries, h0)" ] ;

src/accountant.rs

@@ -25,7 +25,7 @@ pub type Result<T> = result::Result<T, AccountingError>;
 pub struct Accountant {
     pub historian: Historian<u64>,
     pub balances: HashMap<PublicKey, u64>,
-    pub end_hash: Sha256Hash,
+    pub last_id: Sha256Hash,
 }
 
 impl Accountant {
@@ -35,7 +35,7 @@ impl Accountant {
         let mut acc = Accountant {
             historian: hist,
             balances: HashMap::new(),
-            end_hash: start_hash,
+            last_id: start_hash,
         };
         for (i, event) in gen.create_events().into_iter().enumerate() {
             acc.process_verified_event(event, i < 2).unwrap();
@@ -50,7 +50,7 @@ impl Accountant {
         }
 
         if let Some(last_entry) = entries.last() {
-            self.end_hash = last_entry.end_hash;
+            self.last_id = last_entry.id;
         }
 
         entries

src/bin/genesis-block.rs

@@ -22,7 +22,7 @@ fn main() {
     drop(logger.sender);
 
     let entries = receiver.iter().collect::<Vec<_>>();
-    verify_slice_u64(&entries, &entries[0].end_hash);
+    verify_slice_u64(&entries, &entries[0].id);
     println!("[");
     let len = entries.len();
     for (i, x) in entries.iter().enumerate() {

src/event.rs

@@ -2,9 +2,9 @@
 //! an ordered log of events in time.
 
 /// Each log entry contains three pieces of data. The 'num_hashes' field is the number
-/// of hashes performed since the previous entry.  The 'end_hash' field is the result
-/// of hashing 'end_hash' from the previous entry 'num_hashes' times.  The 'event'
-/// field points to an Event that took place shortly after 'end_hash' was generated.
+/// of hashes performed since the previous entry.  The 'id' field is the result
+/// of hashing 'id' from the previous entry 'num_hashes' times.  The 'event'
+/// field points to an Event that took place shortly after 'id' was generated.
 ///
 /// If you divide 'num_hashes' by the amount of time it takes to generate a new hash, you
 /// get a duration estimate since the last event. Since processing power increases
@@ -27,7 +27,7 @@ pub type Signature = GenericArray<u8, U64>;
 /// When 'event' is Tick, the event represents a simple clock tick, and exists for the
 /// sole purpose of improving the performance of event log verification. A tick can
 /// be generated in 'num_hashes' hashes and verified in 'num_hashes' hashes.  By logging
-/// a hash alongside the tick, each tick and be verified in parallel using the 'end_hash'
+/// a hash alongside the tick, each tick and be verified in parallel using the 'id'
 /// of the preceding tick to seed its hashing.
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
 pub enum Event<T> {

src/historian.rs

@@ -53,7 +53,7 @@ impl<T: 'static + Serialize + Clone + Debug + Send> Historian<T> {
                 if let Err(err) = logger.log_events(now, ms_per_tick) {
                     return err;
                 }
-                logger.end_hash = hash(&logger.end_hash);
+                logger.last_id = hash(&logger.last_id);
                 logger.num_hashes += 1;
             }
         })

src/log.rs

@@ -2,9 +2,9 @@
 //! an ordered log of events in time.
 
 /// Each log entry contains three pieces of data. The 'num_hashes' field is the number
-/// of hashes performed since the previous entry.  The 'end_hash' field is the result
-/// of hashing 'end_hash' from the previous entry 'num_hashes' times.  The 'event'
-/// field points to an Event that took place shortly after 'end_hash' was generated.
+/// of hashes performed since the previous entry.  The 'id' field is the result
+/// of hashing 'id' from the previous entry 'num_hashes' times.  The 'event'
+/// field points to an Event that took place shortly after 'id' was generated.
 ///
 /// If you divide 'num_hashes' by the amount of time it takes to generate a new hash, you
 /// get a duration estimate since the last event. Since processing power increases
@@ -26,17 +26,17 @@ pub type Sha256Hash = GenericArray<u8, U32>;
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
 pub struct Entry<T> {
     pub num_hashes: u64,
-    pub end_hash: Sha256Hash,
+    pub id: Sha256Hash,
     pub event: Event<T>,
 }
 
 impl<T> Entry<T> {
     /// Creates a Entry from the number of hashes 'num_hashes' since the previous event
-    /// and that resulting 'end_hash'.
-    pub fn new_tick(num_hashes: u64, end_hash: &Sha256Hash) -> Self {
+    /// and that resulting 'id'.
+    pub fn new_tick(num_hashes: u64, id: &Sha256Hash) -> Self {
         Entry {
             num_hashes,
-            end_hash: *end_hash,
+            id: *id,
             event: Event::Tick,
         }
     }
@@ -50,16 +50,16 @@ pub fn hash(val: &[u8]) -> Sha256Hash {
 }
 
 /// Return the hash of the given hash extended with the given value.
-pub fn extend_and_hash(end_hash: &Sha256Hash, val: &[u8]) -> Sha256Hash {
-    let mut hash_data = end_hash.to_vec();
+pub fn extend_and_hash(id: &Sha256Hash, val: &[u8]) -> Sha256Hash {
+    let mut hash_data = id.to_vec();
     hash_data.extend_from_slice(val);
     hash(&hash_data)
 }
 
-pub fn hash_event<T>(end_hash: &Sha256Hash, event: &Event<T>) -> Sha256Hash {
+pub fn hash_event<T>(id: &Sha256Hash, event: &Event<T>) -> Sha256Hash {
     match get_signature(event) {
-        None => *end_hash,
-        Some(sig) => extend_and_hash(end_hash, &sig),
+        None => *id,
+        Some(sig) => extend_and_hash(id, &sig),
     }
 }
 
@@ -69,11 +69,11 @@ pub fn next_hash<T: Serialize>(
     num_hashes: u64,
     event: &Event<T>,
 ) -> Sha256Hash {
-    let mut end_hash = *start_hash;
+    let mut id = *start_hash;
     for _ in 0..num_hashes {
-        end_hash = hash(&end_hash);
+        id = hash(&id);
     }
-    hash_event(&end_hash, event)
+    hash_event(&id, event)
 }
 
 /// Creates the next Tick Entry 'num_hashes' after 'start_hash'.
@@ -84,7 +84,7 @@ pub fn next_entry<T: Serialize>(
 ) -> Entry<T> {
     Entry {
         num_hashes,
-        end_hash: next_hash(start_hash, num_hashes, &event),
+        id: next_hash(start_hash, num_hashes, &event),
         event,
     }
 }
@@ -96,7 +96,7 @@ pub fn next_entry_mut<T: Serialize>(
     event: Event<T>,
 ) -> Entry<T> {
     let entry = next_entry(start_hash, num_hashes, event);
-    *start_hash = entry.end_hash;
+    *start_hash = entry.id;
     entry
 }
 
@@ -105,34 +105,34 @@ pub fn next_tick<T: Serialize>(start_hash: &Sha256Hash, num_hashes: u64) -> Entr
     next_entry(start_hash, num_hashes, Event::Tick)
 }
 
-/// Verifies self.end_hash is the result of hashing a 'start_hash' 'self.num_hashes' times.
+/// Verifies self.id is the result of hashing a 'start_hash' 'self.num_hashes' times.
 /// If the event is not a Tick, then hash that as well.
 pub fn verify_entry<T: Serialize>(entry: &Entry<T>, start_hash: &Sha256Hash) -> bool {
     if !verify_event(&entry.event) {
         return false;
     }
-    entry.end_hash == next_hash(start_hash, entry.num_hashes, &entry.event)
+    entry.id == next_hash(start_hash, entry.num_hashes, &entry.event)
 }
 
 /// Verifies the hashes and counts of a slice of events are all consistent.
 pub fn verify_slice(events: &[Entry<Sha256Hash>], start_hash: &Sha256Hash) -> bool {
     let genesis = [Entry::new_tick(Default::default(), start_hash)];
     let event_pairs = genesis.par_iter().chain(events).zip(events);
-    event_pairs.all(|(x0, x1)| verify_entry(&x1, &x0.end_hash))
+    event_pairs.all(|(x0, x1)| verify_entry(&x1, &x0.id))
 }
 
 /// Verifies the hashes and counts of a slice of events are all consistent.
 pub fn verify_slice_u64(events: &[Entry<u64>], start_hash: &Sha256Hash) -> bool {
     let genesis = [Entry::new_tick(Default::default(), start_hash)];
     let event_pairs = genesis.par_iter().chain(events).zip(events);
-    event_pairs.all(|(x0, x1)| verify_entry(&x1, &x0.end_hash))
+    event_pairs.all(|(x0, x1)| verify_entry(&x1, &x0.id))
 }
 
 /// Verifies the hashes and events serially. Exists only for reference.
 pub fn verify_slice_seq<T: Serialize>(events: &[Entry<T>], start_hash: &Sha256Hash) -> bool {
     let genesis = [Entry::new_tick(0, start_hash)];
     let mut event_pairs = genesis.iter().chain(events).zip(events);
-    event_pairs.all(|(x0, x1)| verify_entry(&x1, &x0.end_hash))
+    event_pairs.all(|(x0, x1)| verify_entry(&x1, &x0.id))
 }
 
 pub fn create_entries<T: Serialize>(
@@ -140,10 +140,10 @@ pub fn create_entries<T: Serialize>(
     num_hashes: u64,
     events: Vec<Event<T>>,
 ) -> Vec<Entry<T>> {
-    let mut end_hash = *start_hash;
+    let mut id = *start_hash;
     events
         .into_iter()
-        .map(|event| next_entry_mut(&mut end_hash, num_hashes, event))
+        .map(|event| next_entry_mut(&mut id, num_hashes, event))
         .collect()
 }
 
@@ -153,10 +153,10 @@ pub fn create_ticks(
     num_hashes: u64,
     len: usize,
 ) -> Vec<Entry<Sha256Hash>> {
-    let mut end_hash = *start_hash;
+    let mut id = *start_hash;
     iter::repeat(Event::Tick)
         .take(len)
-        .map(|event| next_entry_mut(&mut end_hash, num_hashes, event))
+        .map(|event| next_entry_mut(&mut id, num_hashes, event))
         .collect()
 }
 
@@ -189,7 +189,7 @@ mod tests {
         assert!(verify_slice(&create_ticks(&zero, 0, 2), &zero)); // inductive step
 
         let mut bad_ticks = create_ticks(&zero, 0, 2);
-        bad_ticks[1].end_hash = one;
+        bad_ticks[1].id = one;
         assert!(!verify_slice(&bad_ticks, &zero)); // inductive step, bad
     }
 

src/logger.rs

@@ -22,7 +22,7 @@ pub enum ExitReason {
 pub struct Logger<T> {
     pub sender: SyncSender<Entry<T>>,
     pub receiver: Receiver<Event<T>>,
-    pub end_hash: Sha256Hash,
+    pub last_id: Sha256Hash,
     pub num_hashes: u64,
     pub num_ticks: u64,
 }
@@ -52,16 +52,16 @@ impl<T: Serialize + Clone + Debug> Logger<T> {
         Logger {
             receiver,
             sender,
-            end_hash: start_hash,
+            last_id: start_hash,
             num_hashes: 0,
             num_ticks: 0,
         }
     }
 
     pub fn log_event(&mut self, event: Event<T>) -> Result<(), (Entry<T>, ExitReason)> {
-        self.end_hash = hash_event(&self.end_hash, &event);
+        self.last_id = hash_event(&self.last_id, &event);
         let entry = Entry {
-            end_hash: self.end_hash,
+            id: self.last_id,
             num_hashes: self.num_hashes,
             event,
         };
@@ -93,7 +93,7 @@ impl<T: Serialize + Clone + Debug> Logger<T> {
                 }
                 Err(TryRecvError::Disconnected) => {
                     let entry = Entry {
-                        end_hash: self.end_hash,
+                        id: self.last_id,
                         num_hashes: self.num_hashes,
                         event: Event::Tick,
                     };
@@ -148,12 +148,12 @@ mod tests {
     #[test]
     fn test_genesis_no_creators() {
         let entries = run_genesis(Genesis::new(100, vec![]));
-        assert!(verify_slice_u64(&entries, &entries[0].end_hash));
+        assert!(verify_slice_u64(&entries, &entries[0].id));
     }
 
     #[test]
     fn test_genesis() {
         let entries = run_genesis(Genesis::new(100, vec![Creator::new(42)]));
-        assert!(verify_slice_u64(&entries, &entries[0].end_hash));
+        assert!(verify_slice_u64(&entries, &entries[0].id));
     }
 }