feat(native-currency): Time-lock half of coinbase

The tokenomics of Neptune Cash stipulate that half of all mining
be time-locked for three years. This commit time-locks half of the
coinbase. Half of the guesser fee is already automatically
time-locked.

Specifically, this commit modifies the tasm code for consensus program
`NativeCurrency` to verify that across all outputs (and counting half
of the transaction fee), at least half of the coinbase is time-locked
for three years.

Co-authored-by: Thorkil Schmidiger <[email protected]>

Cargo.toml

@@ -212,3 +212,6 @@ harness = false
 [[bench]]
 name = "consensus"
 harness = false
+
+[patch.crates-io]
+tasm-lib = { git = "https://github.com/TritonVM/tasm-lib.git", rev = "bc50c3320b7ca7527a0066e2b28455f4b4e18003" }

src/models/blockchain/transaction/primitive_witness.rs

@@ -4,6 +4,7 @@ use std::fmt::Display;
 use get_size::GetSize;
 use itertools::Itertools;
 use num_traits::CheckedSub;
+use num_traits::Zero;
 use proptest::arbitrary::Arbitrary;
 use proptest::collection::vec;
 use proptest::strategy::BoxedStrategy;
@@ -439,7 +440,7 @@ impl PrimitiveWitness {
         )
             .prop_flat_map(
                 move |(
-                    total_amount,
+                    mut total_amount,
                     input_address_seeds,
                     input_dist,
                     output_address_seeds,
@@ -471,8 +472,12 @@ impl PrimitiveWitness {
                                 .skip(1)
                                 .cloned()
                                 .sum::<NeptuneCoins>();
-                            *input_amounts.last_mut().unwrap() =
-                                total_amount.checked_sub(&sum_of_all_but_last).unwrap();
+                            if let Some(last_input) = input_amounts.last_mut() {
+                                *last_input =
+                                    total_amount.checked_sub(&sum_of_all_but_last).unwrap();
+                            } else {
+                                total_amount = NeptuneCoins::zero();
+                            }
 
                             let (input_utxos, input_lock_scripts_and_witnesses) =
                                 Self::transaction_inputs_from_address_seeds_and_amounts(
@@ -503,7 +508,11 @@ impl PrimitiveWitness {
                         .map(|utxo| utxo.get_native_currency_amount())
                         .sum::<NeptuneCoins>();
 
-                    assert_eq!(maybe_coinbase.unwrap_or(total_inputs), total_outputs + fee);
+                    assert_eq!(
+                        maybe_coinbase.unwrap_or(total_inputs),
+                        total_outputs + fee,
+                        "total outputs: {total_outputs:?} fee: {fee:?}"
+                    );
 
                     let output_utxos = Self::valid_tx_outputs_from_amounts_and_address_seeds(
                         &output_amounts,
@@ -1215,7 +1224,6 @@ mod test {
         #[strategy(PrimitiveWitness::arbitrary_with_size_numbers(Some(2), 2, 2))]
         primitive_witness: PrimitiveWitness,
     ) {
-        println!("generated primitive witness.");
         let mut total = if let Some(amount) = primitive_witness.kernel.coinbase {
             amount
         } else {

src/models/blockchain/transaction/transaction_kernel.rs

@@ -24,11 +24,11 @@ use crate::util_types::mutator_set::removal_record::RemovalRecord;
 
 /// TransactionKernel is immutable and its hash never changes.
 ///
-/// See [TransactionKernelModifier] for generating modified copies.
+/// See [`TransactionKernelModifier`] for generating modified copies.
 #[derive(Clone, Debug, Serialize, Deserialize, Eq, GetSize, BFieldCodec, TasmObject)]
 #[readonly::make]
 pub struct TransactionKernel {
-    // note: see field descriptions in TransactionKernelProxy
+    // note: see field descriptions in [`TransactionKernelProxy`]
     pub inputs: Vec<RemovalRecord>,
     pub outputs: Vec<AdditionRecord>,
     pub public_announcements: Vec<PublicAnnouncement>,

src/models/blockchain/transaction/utxo.rs

@@ -244,7 +244,7 @@ impl<'a> Arbitrary<'a> for Utxo {
     }
 }
 #[cfg(test)]
-mod utxo_tests {
+mod test {
     use proptest::prelude::*;
     use rand::thread_rng;
     use rand::Rng;