SMT storage: protection against second preimage

crates/contracts/Cargo.toml

@@ -10,11 +10,10 @@ keywords = ["simplicity", "liquid", "bitcoin", "elements", "contracts"]
 categories = ["cryptography::cryptocurrencies"]
 
 [features]
-default = ["simple-storage", "bytes32-tr-storage", "array-tr-storage", "smt-storage"]
+default = ["simple-storage", "bytes32-tr-storage", "array-tr-storage"]
 simple-storage = []
 bytes32-tr-storage = []
 array-tr-storage = []
-smt-storage = []
 
 [lints]
 workspace = true

crates/contracts/README.md

@@ -9,7 +9,15 @@ Current contract modules in this crate:
     - [Simple Storage](src/state_management/simple_storage)
     - [Bytes32 Taproot Storage](src/state_management/bytes32_tr_storage)
     - [Array Taproot Storage](src/state_management/array_tr_storage)
-    - [Sparse Merkle Tree Storage](src/state_management/smt_storage)
+
+> [!NOTE]
+> Sparse Merkle Tree Storage was removed from the crate. The implementation
+> with domain-separated `SMT/1.0/leaf` and `SMT/1.0/node` tagged hashes is
+> preserved in the
+> [`smt_storage` directory](https://github.com/BlockstreamResearch/simplicity-contracts/tree/24bdb8b4eed3b9ed311570c3143461d9c85e19ed/crates/contracts/src/state_management/smt_storage).
+>
+> For more details, see
+> [PR #72](https://github.com/BlockstreamResearch/simplicity-contracts/pull/72).
 
 - Finance:
   - [Options](src/programs/options.rs)

crates/contracts/src/lib.rs

@@ -13,7 +13,5 @@ pub use state_management::array_tr_storage;
 pub use state_management::bytes32_tr_storage;
 #[cfg(feature = "simple-storage")]
 pub use state_management::simple_storage;
-#[cfg(feature = "smt-storage")]
-pub use state_management::smt_storage;
 
 pub use simplicityhl_core::*;

crates/contracts/src/state_management/mod.rs

@@ -4,5 +4,3 @@ pub mod array_tr_storage;
 pub mod bytes32_tr_storage;
 #[cfg(feature = "simple-storage")]
 pub mod simple_storage;
-#[cfg(feature = "smt-storage")]
-pub mod smt_storage;