Add signatures

Cargo.toml

@@ -29,3 +29,5 @@ sha2-asm = {version="0.3", optional=true}
 generic-array = { version = "0.9.0", default-features = false, features = ["serde"] }
 serde = "1.0.27"
 serde_derive = "1.0.27"
+ring = "0.12.1"
+untrusted = "0.5.1"

README.md

@@ -37,7 +37,7 @@ use std::sync::mpsc::SendError;
 
 fn create_log(hist: &Historian) -> Result<(), SendError<Event>> {
     sleep(Duration::from_millis(15));
-    hist.sender.send(Event::UserDataKey(Sha256Hash::default()))?;
+    hist.sender.send(Event::Discovery(Sha256Hash::default()))?;
     sleep(Duration::from_millis(10));
     Ok(())
 }
@@ -62,7 +62,7 @@ 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: UserDataKey(3735928559) }
+Entry { num_hashes: 2, end_hash: [67, ...], event: Discovery(3735928559) }
 Entry { num_hashes: 3, end_hash: [123, ...], event: Tick }
 ```
 

diagrams/historian.msc

@@ -4,10 +4,10 @@ msc {
   logger=>historian [ label = "e0 = Entry{hash: h0, n: 0, event: Tick}" ] ;
   logger=>logger [ label = "h1 = hash(h0)" ] ;
   logger=>logger [ label = "h2 = hash(h1)" ] ;
-  client=>historian [ label = "UserData(d0)" ] ;
-  historian=>logger [ label = "UserData(d0)" ] ;
+  client=>historian [ label = "Discovery(d0)" ] ;
+  historian=>logger [ label = "Discovery(d0)" ] ;
   logger=>logger [ label = "h3 = hash(h2 + d0)" ] ;
-  logger=>historian [ label = "e1 = Entry{hash: hash(h3), n: 2, event: UserData(d0)}" ] ;
+  logger=>historian [ label = "e1 = Entry{hash: hash(h3), n: 2, event: Discovery(d0)}" ] ;
   logger=>logger [ label = "h4 = hash(h3)" ] ;
   logger=>logger [ label = "h5 = hash(h4)" ] ;
   logger=>logger [ label = "h6 = hash(h5)" ] ;

src/bin/demo.rs

@@ -8,7 +8,7 @@ use std::sync::mpsc::SendError;
 
 fn create_log(hist: &Historian) -> Result<(), SendError<Event>> {
     sleep(Duration::from_millis(15));
-    hist.sender.send(Event::UserDataKey(Sha256Hash::default()))?;
+    hist.sender.send(Event::Discovery(Sha256Hash::default()))?;
     sleep(Duration::from_millis(10));
     Ok(())
 }

src/historian.rs

@@ -8,7 +8,7 @@
 use std::thread::JoinHandle;
 use std::sync::mpsc::{Receiver, Sender};
 use std::time::{Duration, SystemTime};
-use log::{extend_and_hash, hash, Entry, Event, Sha256Hash};
+use log::{hash, hash_event, Entry, Event, Sha256Hash};
 
 pub struct Historian {
     pub sender: Sender<Event>,
@@ -27,9 +27,7 @@ fn log_event(
     end_hash: &mut Sha256Hash,
     event: Event,
 ) -> Result<(), (Entry, ExitReason)> {
-    if let Event::UserDataKey(key) = event {
-        *end_hash = extend_and_hash(end_hash, &key);
-    }
+    *end_hash = hash_event(end_hash, &event);
     let entry = Entry {
         end_hash: *end_hash,
         num_hashes: *num_hashes,
@@ -139,7 +137,7 @@ mod tests {
 
         hist.sender.send(Event::Tick).unwrap();
         sleep(Duration::new(0, 1_000_000));
-        hist.sender.send(Event::UserDataKey(zero)).unwrap();
+        hist.sender.send(Event::Discovery(zero)).unwrap();
         sleep(Duration::new(0, 1_000_000));
         hist.sender.send(Event::Tick).unwrap();
 
@@ -173,7 +171,7 @@ mod tests {
         let zero = Sha256Hash::default();
         let hist = Historian::new(&zero, Some(20));
         sleep(Duration::from_millis(30));
-        hist.sender.send(Event::UserDataKey(zero)).unwrap();
+        hist.sender.send(Event::Discovery(zero)).unwrap();
         sleep(Duration::from_millis(15));
         drop(hist.sender);
         assert_eq!(

src/lib.rs

@@ -3,7 +3,9 @@ pub mod log;
 pub mod historian;
 extern crate generic_array;
 extern crate rayon;
+extern crate ring;
 extern crate serde;
 #[macro_use]
 extern crate serde_derive;
 extern crate sha2;
+extern crate untrusted;

src/log.rs

@@ -14,8 +14,11 @@
 /// was generated by the fastest processor at the time the entry was logged.
 
 use generic_array::GenericArray;
-use generic_array::typenum::U32;
+use generic_array::typenum::{U32, U64};
+use ring::signature::Ed25519KeyPair;
 pub type Sha256Hash = GenericArray<u8, U32>;
+pub type PublicKey = GenericArray<u8, U32>;
+pub type Signature = GenericArray<u8, U64>;
 
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
 pub struct Entry {
@@ -32,7 +35,12 @@ pub struct Entry {
 #[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
 pub enum Event {
     Tick,
-    UserDataKey(Sha256Hash),
+    Discovery(Sha256Hash),
+    Claim {
+        key: PublicKey,
+        data: Sha256Hash,
+        sig: Signature,
+    },
 }
 
 impl Entry {
@@ -47,12 +55,30 @@ impl Entry {
     }
 
     /// Verifies self.end_hash is the result of hashing a 'start_hash' 'self.num_hashes' times.
-    /// If the event is a UserDataKey, then hash that as well.
+    /// If the event is not a Tick, then hash that as well.
     pub fn verify(self: &Self, start_hash: &Sha256Hash) -> bool {
+        if let Event::Claim { key, data, sig } = self.event {
+            if !verify_signature(&key, &data, &sig) {
+                return false;
+            }
+        }
         self.end_hash == next_hash(start_hash, self.num_hashes, &self.event)
     }
 }
 
+/// Return a Claim Event for the given hash and key-pair.
+pub fn sign_hash(data: &Sha256Hash, key_pair: &Ed25519KeyPair) -> Event {
+    let sig = key_pair.sign(data);
+    let peer_public_key_bytes = key_pair.public_key_bytes();
+    let sig_bytes = sig.as_ref();
+    Event::Claim {
+        key: GenericArray::clone_from_slice(peer_public_key_bytes),
+        data: GenericArray::clone_from_slice(data),
+        sig: GenericArray::clone_from_slice(sig_bytes),
+    }
+}
+
+/// Return a Sha256 hash for the given data.
 pub fn hash(val: &[u8]) -> Sha256Hash {
     use sha2::{Digest, Sha256};
     let mut hasher = Sha256::default();
@@ -61,21 +87,32 @@ 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 {
+pub fn extend_and_hash(end_hash: &Sha256Hash, ty: u8, val: &[u8]) -> Sha256Hash {
     let mut hash_data = end_hash.to_vec();
+    hash_data.push(ty);
     hash_data.extend_from_slice(val);
     hash(&hash_data)
 }
 
+pub fn hash_event(end_hash: &Sha256Hash, event: &Event) -> Sha256Hash {
+    match *event {
+        Event::Tick => *end_hash,
+        Event::Discovery(data) => extend_and_hash(end_hash, 1, &data),
+        Event::Claim { key, data, sig } => {
+            let mut event_data = data.to_vec();
+            event_data.extend_from_slice(&sig);
+            event_data.extend_from_slice(&key);
+            extend_and_hash(end_hash, 2, &event_data)
+        }
+    }
+}
+
 pub fn next_hash(start_hash: &Sha256Hash, num_hashes: u64, event: &Event) -> Sha256Hash {
     let mut end_hash = *start_hash;
     for _ in 0..num_hashes {
         end_hash = hash(&end_hash);
     }
-    if let Event::UserDataKey(key) = *event {
-        return extend_and_hash(&end_hash, &key);
-    }
-    end_hash
+    hash_event(&end_hash, event)
 }
 
 /// Creates the next Tick Entry 'num_hashes' after 'start_hash'.
@@ -107,6 +144,16 @@ pub fn verify_slice_seq(events: &[Entry], start_hash: &Sha256Hash) -> bool {
     event_pairs.all(|(x0, x1)| x1.verify(&x0.end_hash))
 }
 
+/// Verify a signed message with the given public key.
+pub fn verify_signature(peer_public_key_bytes: &[u8], msg_bytes: &[u8], sig_bytes: &[u8]) -> bool {
+    use untrusted;
+    use ring::signature;
+    let peer_public_key = untrusted::Input::from(peer_public_key_bytes);
+    let msg = untrusted::Input::from(msg_bytes);
+    let sig = untrusted::Input::from(sig_bytes);
+    signature::verify(&signature::ED25519, peer_public_key, msg, sig).is_ok()
+}
+
 /// Create a vector of Ticks of length 'len' from 'start_hash' hash and 'num_hashes'.
 pub fn create_ticks(start_hash: &Sha256Hash, num_hashes: u64, len: usize) -> Vec<Entry> {
     use std::iter;
@@ -169,9 +216,9 @@ mod tests {
         let zero = Sha256Hash::default();
         let one = hash(&zero);
 
-        // First, verify UserData events
+        // First, verify Discovery events
         let mut end_hash = zero;
-        let events = [Event::UserDataKey(zero), Event::UserDataKey(one)];
+        let events = [Event::Discovery(zero), Event::Discovery(one)];
         let mut entries: Vec<Entry> = events
             .iter()
             .map(|event| {
@@ -180,16 +227,66 @@ mod tests {
                 entry
             })
             .collect();
-        assert!(verify_slice(&entries, &zero)); // inductive step
+        assert!(verify_slice(&entries, &zero));
 
-        // Next, swap only two UserData events and ensure verification fails.
+        // Next, swap two Discovery events and ensure verification fails.
         let event0 = entries[0].event.clone();
         let event1 = entries[1].event.clone();
         entries[0].event = event1;
         entries[1].event = event0;
-        assert!(!verify_slice(&entries, &zero)); // inductive step
+        assert!(!verify_slice(&entries, &zero));
     }
 
+    #[test]
+    fn test_signature() {
+        use untrusted;
+        use ring::{rand, signature};
+        let rng = rand::SystemRandom::new();
+        let pkcs8_bytes = signature::Ed25519KeyPair::generate_pkcs8(&rng).unwrap();
+        let key_pair =
+            signature::Ed25519KeyPair::from_pkcs8(untrusted::Input::from(&pkcs8_bytes)).unwrap();
+        const MESSAGE: &'static [u8] = b"hello, world";
+        let event0 = sign_hash(&hash(MESSAGE), &key_pair);
+        let zero = Sha256Hash::default();
+        let mut end_hash = zero;
+        let entries: Vec<Entry> = [event0]
+            .iter()
+            .map(|event| {
+                let entry = next_entry(&end_hash, 0, event.clone());
+                end_hash = entry.end_hash;
+                entry
+            })
+            .collect();
+        assert!(verify_slice(&entries, &zero));
+    }
+
+    #[test]
+    fn test_bad_signature() {
+        use untrusted;
+        use ring::{rand, signature};
+        let rng = rand::SystemRandom::new();
+        let pkcs8_bytes = signature::Ed25519KeyPair::generate_pkcs8(&rng).unwrap();
+        let key_pair =
+            signature::Ed25519KeyPair::from_pkcs8(untrusted::Input::from(&pkcs8_bytes)).unwrap();
+        const MESSAGE: &'static [u8] = b"hello, world";
+        let mut event0 = sign_hash(&hash(MESSAGE), &key_pair);
+        if let Event::Claim { key, sig, .. } = event0 {
+            const GOODBYE: &'static [u8] = b"goodbye cruel world";
+            let data = hash(GOODBYE);
+            event0 = Event::Claim { key, data, sig };
+        }
+        let zero = Sha256Hash::default();
+        let mut end_hash = zero;
+        let entries: Vec<Entry> = [event0]
+            .iter()
+            .map(|event| {
+                let entry = next_entry(&end_hash, 0, event.clone());
+                end_hash = entry.end_hash;
+                entry
+            })
+            .collect();
+        assert!(!verify_slice(&entries, &zero));
+    }
 }
 
 #[cfg(all(feature = "unstable", test))]