2018-03-30 10:43:38 -07:00
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//! The `entry` module is a fundamental building block of Proof of History. It contains a
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//! unique ID that is the hash of the Entry before it, plus the hash of the
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//! transactions within it. Entries cannot be reordered, and its field `num_hashes`
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2018-03-29 11:20:54 -07:00
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//! represents an approximate amount of time since the last Entry was created.
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2018-06-20 11:40:41 -07:00
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use bincode::serialized_size;
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2018-03-26 21:03:26 -07:00
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use hash::{extend_and_hash, hash, Hash};
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2018-06-20 11:40:41 -07:00
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use packet::BLOB_DATA_SIZE;
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2018-03-28 21:02:47 -07:00
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use rayon::prelude::*;
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2018-05-23 23:29:01 -07:00
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use transaction::Transaction;
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2018-03-06 16:31:17 -08:00
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2018-03-29 11:20:54 -07:00
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/// Each Entry contains three pieces of data. The `num_hashes` field is the number
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/// of hashes performed since the previous entry. The `id` field is the result
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2018-05-25 14:51:41 -07:00
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/// of hashing `id` from the previous entry `num_hashes` times. The `transactions`
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2018-06-06 10:19:56 -07:00
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/// field points to Transactions that took place shortly before `id` was generated.
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2018-03-29 11:20:54 -07:00
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///
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/// If you divide `num_hashes` by the amount of time it takes to generate a new hash, you
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/// get a duration estimate since the last Entry. Since processing power increases
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/// over time, one should expect the duration `num_hashes` represents to decrease proportionally.
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2018-06-06 10:19:56 -07:00
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/// An upper bound on Duration can be estimated by assuming each hash was generated by the
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/// world's fastest processor at the time the entry was recorded. Or said another way, it
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/// is physically not possible for a shorter duration to have occurred if one assumes the
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/// hash was computed by the world's fastest processor at that time. The hash chain is both
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/// a Verifiable Delay Function (VDF) and a Proof of Work (not to be confused with Proof or
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/// Work consensus!)
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2018-03-06 16:31:17 -08:00
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#[derive(Serialize, Deserialize, Debug, PartialEq, Eq, Clone)]
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2018-03-06 19:22:30 -08:00
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pub struct Entry {
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2018-06-06 10:19:56 -07:00
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/// The number of hashes since the previous Entry ID.
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2018-03-06 16:31:17 -08:00
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pub num_hashes: u64,
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2018-06-06 10:19:56 -07:00
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/// The SHA-256 hash `num_hashes` after the previous Entry ID.
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2018-03-06 16:36:45 -08:00
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pub id: Hash,
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2018-06-06 10:19:56 -07:00
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/// An unordered list of transactions that were observed before the Entry ID was
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/// generated. The may have been observed before a previous Entry ID but were
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/// pushed back into this list to ensure deterministic interpretation of the ledger.
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2018-05-25 14:51:41 -07:00
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pub transactions: Vec<Transaction>,
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2018-06-25 23:28:41 -07:00
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/// Indication that:
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/// 1. the next Entry in the ledger has transactions that can potentially
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/// be verified in parallel with these transactions
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/// 2. this Entry can be left out of the bank's entry_id cache for
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/// purposes of duplicate rejection
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pub has_more: bool,
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2018-03-06 16:31:17 -08:00
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}
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2018-03-06 19:22:30 -08:00
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impl Entry {
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2018-05-16 16:49:58 -07:00
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/// Creates the next Entry `num_hashes` after `start_hash`.
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2018-06-25 23:28:41 -07:00
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pub fn new(
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start_hash: &Hash,
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cur_hashes: u64,
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transactions: Vec<Transaction>,
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has_more: bool,
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) -> Self {
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2018-05-25 14:51:41 -07:00
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let num_hashes = cur_hashes + if transactions.is_empty() { 0 } else { 1 };
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let id = next_hash(start_hash, 0, &transactions);
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2018-06-20 11:40:41 -07:00
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let entry = Entry {
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2018-05-16 16:49:58 -07:00
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num_hashes,
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id,
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2018-05-25 14:51:41 -07:00
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transactions,
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2018-06-25 23:28:41 -07:00
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has_more,
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2018-06-20 11:40:41 -07:00
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};
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assert!(serialized_size(&entry).unwrap() <= BLOB_DATA_SIZE as u64);
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entry
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2018-05-16 16:49:58 -07:00
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}
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/// Creates the next Tick Entry `num_hashes` after `start_hash`.
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2018-05-25 14:51:41 -07:00
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pub fn new_mut(
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start_hash: &mut Hash,
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cur_hashes: &mut u64,
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transactions: Vec<Transaction>,
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2018-06-25 23:28:41 -07:00
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has_more: bool,
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2018-05-25 14:51:41 -07:00
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) -> Self {
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2018-06-25 23:28:41 -07:00
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let entry = Self::new(start_hash, *cur_hashes, transactions, has_more);
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2018-05-16 16:49:58 -07:00
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*start_hash = entry.id;
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*cur_hashes = 0;
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2018-06-20 11:40:41 -07:00
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assert!(serialized_size(&entry).unwrap() <= BLOB_DATA_SIZE as u64);
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2018-05-16 16:49:58 -07:00
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entry
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}
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2018-05-25 14:51:41 -07:00
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/// Creates a Entry from the number of hashes `num_hashes` since the previous transaction
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2018-03-22 13:40:28 -07:00
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/// and that resulting `id`.
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2018-03-06 16:36:45 -08:00
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pub fn new_tick(num_hashes: u64, id: &Hash) -> Self {
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2018-03-06 16:31:17 -08:00
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Entry {
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num_hashes,
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id: *id,
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2018-05-25 14:51:41 -07:00
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transactions: vec![],
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2018-06-25 23:28:41 -07:00
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has_more: false,
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2018-03-06 16:31:17 -08:00
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}
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}
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2018-03-22 13:40:28 -07:00
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/// Verifies self.id is the result of hashing a `start_hash` `self.num_hashes` times.
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2018-05-25 14:51:41 -07:00
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/// If the transaction is not a Tick, then hash that as well.
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2018-03-06 16:36:45 -08:00
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pub fn verify(&self, start_hash: &Hash) -> bool {
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2018-05-25 14:51:41 -07:00
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self.transactions.par_iter().all(|tx| tx.verify_plan())
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&& self.id == next_hash(start_hash, self.num_hashes, &self.transactions)
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2018-03-06 16:31:17 -08:00
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}
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}
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2018-05-25 15:05:37 -07:00
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fn add_transaction_data(hash_data: &mut Vec<u8>, tx: &Transaction) {
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2018-05-23 23:29:01 -07:00
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hash_data.push(0u8);
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2018-05-25 15:05:37 -07:00
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hash_data.extend_from_slice(&tx.sig);
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2018-04-02 19:47:48 -07:00
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}
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2018-05-25 14:51:41 -07:00
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/// Creates the hash `num_hashes` after `start_hash`. If the transaction contains
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2018-04-16 13:38:31 -07:00
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/// a signature, the final hash will be a hash of both the previous ID and
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2018-06-18 13:23:15 -07:00
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/// the signature. If num_hashes is zero and there's no transaction data,
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2018-06-21 16:09:17 -07:00
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/// start_hash is returned.
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2018-06-18 13:23:15 -07:00
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fn next_hash(start_hash: &Hash, num_hashes: u64, transactions: &[Transaction]) -> Hash {
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2018-03-06 16:31:17 -08:00
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let mut id = *start_hash;
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2018-03-09 15:16:29 -08:00
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for _ in 1..num_hashes {
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2018-03-06 16:31:17 -08:00
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id = hash(&id);
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}
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2018-03-09 15:16:29 -08:00
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2018-05-25 14:51:41 -07:00
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// Hash all the transaction data
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2018-03-09 15:16:29 -08:00
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let mut hash_data = vec![];
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2018-05-25 14:51:41 -07:00
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for tx in transactions {
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add_transaction_data(&mut hash_data, tx);
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2018-03-06 16:31:17 -08:00
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}
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2018-03-09 15:16:29 -08:00
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if !hash_data.is_empty() {
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2018-04-16 13:38:31 -07:00
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extend_and_hash(&id, &hash_data)
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} else if num_hashes != 0 {
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hash(&id)
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} else {
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id
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2018-03-09 15:16:29 -08:00
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}
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2018-03-06 16:31:17 -08:00
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}
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2018-06-04 16:21:12 -07:00
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/// Creates the next Tick or Transaction Entry `num_hashes` after `start_hash`.
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2018-05-25 14:51:41 -07:00
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pub fn next_entry(start_hash: &Hash, num_hashes: u64, transactions: Vec<Transaction>) -> Entry {
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2018-06-21 16:15:26 -07:00
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assert!(num_hashes > 0 || transactions.len() == 0);
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2018-03-06 16:31:17 -08:00
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Entry {
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num_hashes,
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2018-05-25 14:51:41 -07:00
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id: next_hash(start_hash, num_hashes, &transactions),
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transactions,
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2018-06-25 23:28:41 -07:00
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has_more: false,
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2018-03-06 16:31:17 -08:00
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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2018-04-02 20:07:38 -07:00
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use chrono::prelude::*;
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2018-05-16 16:49:58 -07:00
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use entry::Entry;
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2018-03-09 16:02:17 -08:00
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use hash::hash;
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use signature::{KeyPair, KeyPairUtil};
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2018-05-23 22:53:10 -07:00
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use transaction::Transaction;
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2018-03-06 16:31:17 -08:00
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#[test]
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2018-03-09 16:02:17 -08:00
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fn test_entry_verify() {
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2018-03-06 16:36:45 -08:00
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let zero = Hash::default();
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2018-03-06 16:31:17 -08:00
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let one = hash(&zero);
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2018-03-06 19:22:30 -08:00
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assert!(Entry::new_tick(0, &zero).verify(&zero)); // base case
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assert!(!Entry::new_tick(0, &zero).verify(&one)); // base case, bad
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2018-05-11 08:45:42 -07:00
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assert!(next_entry(&zero, 1, vec![]).verify(&zero)); // inductive step
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assert!(!next_entry(&zero, 1, vec![]).verify(&one)); // inductive step, bad
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2018-03-06 16:31:17 -08:00
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}
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2018-03-09 16:02:17 -08:00
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#[test]
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2018-05-25 14:51:41 -07:00
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fn test_transaction_reorder_attack() {
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2018-03-09 16:02:17 -08:00
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let zero = Hash::default();
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// First, verify entries
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let keypair = KeyPair::new();
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2018-05-29 09:12:27 -07:00
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let tx0 = Transaction::new(&keypair, keypair.pubkey(), 0, zero);
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let tx1 = Transaction::new(&keypair, keypair.pubkey(), 1, zero);
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2018-06-25 23:28:41 -07:00
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let mut e0 = Entry::new(&zero, 0, vec![tx0.clone(), tx1.clone()], false);
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2018-03-09 16:02:17 -08:00
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assert!(e0.verify(&zero));
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2018-05-25 14:51:41 -07:00
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// Next, swap two transactions and ensure verification fails.
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2018-05-29 09:12:27 -07:00
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e0.transactions[0] = tx1; // <-- attack
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e0.transactions[1] = tx0;
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2018-03-09 16:02:17 -08:00
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assert!(!e0.verify(&zero));
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}
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2018-04-02 20:07:38 -07:00
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#[test]
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fn test_witness_reorder_attack() {
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let zero = Hash::default();
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// First, verify entries
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let keypair = KeyPair::new();
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2018-05-29 09:12:27 -07:00
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let tx0 = Transaction::new_timestamp(&keypair, Utc::now(), zero);
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let tx1 = Transaction::new_signature(&keypair, Default::default(), zero);
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2018-06-25 23:28:41 -07:00
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let mut e0 = Entry::new(&zero, 0, vec![tx0.clone(), tx1.clone()], false);
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2018-04-02 20:07:38 -07:00
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assert!(e0.verify(&zero));
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2018-05-25 14:51:41 -07:00
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// Next, swap two witness transactions and ensure verification fails.
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2018-05-29 09:12:27 -07:00
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e0.transactions[0] = tx1; // <-- attack
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e0.transactions[1] = tx0;
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2018-04-02 20:07:38 -07:00
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assert!(!e0.verify(&zero));
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}
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2018-03-06 16:31:17 -08:00
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#[test]
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2018-05-11 08:45:42 -07:00
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fn test_next_entry() {
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2018-03-06 16:36:45 -08:00
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let zero = Hash::default();
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2018-05-11 09:34:46 -07:00
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let tick = next_entry(&zero, 1, vec![]);
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2018-04-16 13:38:31 -07:00
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assert_eq!(tick.num_hashes, 1);
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assert_ne!(tick.id, zero);
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2018-06-18 13:23:15 -07:00
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let tick = next_entry(&zero, 0, vec![]);
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assert_eq!(tick.num_hashes, 0);
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assert_eq!(tick.id, zero);
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2018-06-20 11:40:41 -07:00
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let keypair = KeyPair::new();
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let tx0 = Transaction::new_timestamp(&keypair, Utc::now(), zero);
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let entry0 = next_entry(&zero, 1, vec![tx0.clone()]);
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assert_eq!(entry0.num_hashes, 1);
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assert_eq!(entry0.id, next_hash(&zero, 1, &vec![tx0]));
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2018-03-06 16:31:17 -08:00
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}
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2018-06-21 16:15:26 -07:00
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#[test]
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#[should_panic]
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fn test_next_entry_panic() {
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let zero = Hash::default();
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let keypair = KeyPair::new();
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let tx = Transaction::new(&keypair, keypair.pubkey(), 0, zero);
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next_entry(&zero, 0, vec![tx]);
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}
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2018-03-06 16:31:17 -08:00
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}
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