Merge pull request #204 from RGB-WG/vesper

Audit and refactoring of commitments workflows. Vesper support
RGB-WG · Feb 26, 2024 · d7e42b2 · d7e42b2
2 parents 99c5318 + d4f96c9
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diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -22,10 +22,10 @@ name = "rgbcore-stl"
 required-features = ["stl"]
 
 [dependencies]
-amplify = { version = "~4.5.0", features = ["rand"] }
-strict_encoding = "~2.6.2"
-strict_types = "~1.6.3"
-aluvm = { version = "~0.11.0-beta.2", features = ["std"] }
+amplify = { version = "~4.6.0", features = ["rand"] }
+strict_encoding = "~2.7.0-beta.1"
+strict_types = "~2.7.0-beta.1"
+aluvm = { version = "~0.11.0-beta.3", features = ["std"] }
 commit_verify = { version = "~0.11.0-beta.3", features = ["rand", "derive"] }
 single_use_seals = "~0.11.0-beta.3"
 bp-core = { version = "~0.11.0-beta.3" }
@@ -62,4 +62,9 @@ wasm-bindgen-test = "0.3"
 features = [ "all" ]
 
 [patch.crates-io]
+strict_types = { git = "https://github.com/strict-types/strict-types", branch = "vesper" }
+commit_verify = { git = "https://github.com/LNP-BP/client_side_validation", branch = "layouts" }
+bp-consensus = { git = "https://github.com/BP-WG/bp-core", branch = "v0.11" }
+bp-dbc = { git = "https://github.com/BP-WG/bp-core", branch = "v0.11" }
+bp-seals = { git = "https://github.com/BP-WG/bp-core", branch = "v0.11" }
 bp-core = { git = "https://github.com/BP-WG/bp-core", branch = "v0.11" }
diff --git a/doc/Commitments.md b/doc/Commitments.md
@@ -0,0 +1,275 @@
+# RGB consensus commitments
+
+RGB commits to client-side validated data using dedicated serialization 
+mechanism, implemented via `CommitEncode` trait. Depending on the specific data,
+the mechanism can be is partially or completely different from strict 
+serialization, used for data storage. For instance, all data which may be 
+confidential must be concealed, such that parties having no access to the 
+original non-confidential values still be able to generate the same 
+deterministic commitment value and verify single-use seals.
+
+Any final consensus commitment is a SHA256 tagged hash. The tagging is performed
+according to BIP-340, when a commitment-specific fixed ASCII string value is 
+first hashed with a single SHA256 hash, and the resulting 32 bytes are feed into
+a new SHA256 hasher twice before any actual data.
+
+
+## Generating commitment id
+
+The commitment mechanism uses traits from [`commit_verify`] crate, specifically 
+its `id.rs`and `merkle.rs` modules.
+
+### `CommitEncode` trait
+
+It is the main trait which must be implemented for each type requiring a 
+dedicated commitment id. 
+
+The trait implementation can be done either with derive macro 
+`#[derive(CommitEncode)]` or by providing a manual implementation.
+
+The derive macro takes two arguments: `strategy` and `id`:
+- `id` must specify a resulting commitment id type, i.e. type wrapping 32-byte 
+  tagged SHA256 hash, implementing `CommitmentId` trait (the implementation 
+  provides a tag for the hasher - see trait details below). The type must also 
+  provide a converting constructor from `coommit_verify::Sha256` hasher.
+- `strategy` specifies a workflow used to feed the type data to the SHA256 
+  tagged hasher:
+  * `strategy = strict`: the hasher receive strict-serialized type;
+  * `strategy = conceal`: the type data are first concealed, and only then are 
+    strict-serialized into the hasher.
+
+Manual `CommitEncode` implementation must be provided only when the commitment
+procedure is custom and can't be implemented using any of the strategies, for
+instance when a collection must be merklized (see on merklization below).
+
+NB: you should never call methods of `CommitEncode` trait directly, and instead
+use `CommitId` trait, which is automatically implemented for 
+
+### `CommitmentId` trait
+
+Each consensus commitment must have a dedicated Rust newtype, which wraps over
+inner `Bytes32` - a 32-byte resulting tagged hash value. The type is marked as
+a consensus commitment by implementing `CommitmentId` trait for it, which 
+requires to provide a tag string values for the tagged hash.
+
+The hash tags are defined using URN strings in form of 
+`urn:<org>:<protocol>:<data>#<date>`, where `<org>` stands for the organization,
+`<protocol>` is the name of the protocol, `<data>` is the data type name 
+producing the commitment, and `<date>` is a `YYYY-MM-DD` string for the latest
+revision of the commitment layout. 
+
+### `CommitId` trait
+
+This trait is automatically implemented for all types which have `CommitEncode`
+implementation. You can't implement this trait manually and just need to call
+its `CommitId::commit_id()` method to produce the final commitment (i.e. bytes
+of the tagged hash in form of `CommitmentId`-implementing type).
+
+The trait also provides `CommitId::commitment_layout()` method, which can be 
+used for automatically generating the documentation on the commitment workflow.
+
+## Merklization procedure
+
+Merlization procedure uses traits and data types from `merkle.rs` module of
+`commit_verify` crate. It commits to the tree parameters, such as number of 
+elements, depth of the tree, as well as depth of each node; and uses tagged 
+SHA256, like the rest of the commitment procedures used here.
+
+The main data type, related to the merklization, is `MerkleHash`: it is a tagged
+hash (using `urn:ubideco:merkle:node#2024-01-31` tag) representing node at any 
+position of the tree: leaves, branch nodes and merkle tree root. `MerkleHash` 
+can be produced in the following ways:
+- as a result of merklziation procedure, when it represents Merkle tree root;
+- as a root of empty Merkle tree (i.e. collection having 0 elements), by calling
+  `MerkleHash::void(0u8, 0u32)`,
+- as a Merkle leaf, by implementing `CommitEncode` on some type and setting
+  commitment id to be `MerkleHash`.
+
+In all of the above cases the hash commits to the tree parameters, which makes
+it safe to use the same type for leaves, branches and root nodes. Specifically,
+it uses an intermediate structure `MerkleNode`, which is filled with information
+on (see [`MerkleNode.vesper`](../stl/MerkleNode.vesper) for details):
+- type of node branching (no branches, one branch or two branches),
+- depth of the node, as 8-bit unsigned integer,
+- width of the tree at its base, as a 256-bit LE unsigned integer,
+- node hashes of the branches; if one or both branches are absent, they are
+  replaced with 32 bytes of repeated 0xFF value. 
+
+A collection in form of a list (Rust `Vec`) or an ordered set of unique 
+non-repeating items (Rust `BTreeSet`), if wrapped into a confinement (i.e. has
+type-defined bounds on the minimum or maximum number of items) can be 
+automatically merklized when passed as an argument to `MerkleHash::merklize()`
+call. The API puts the following requirements on the collection: either
+- maximum number of elements must be either 0xFF or 0xFFFF **and** each 
+  collection element must implement `CommitEncode` trait with target id set to
+  `MerkleHash`,
+- or there is a manual implementation of `MerkleLeaves` trait.
+
+```mermaid
+flowchart BT
+    subgraph Merklization
+        direction LR
+        subgraph MerkleNode
+            branching
+            depth
+            width
+            node1
+            node2
+        end
+        MerkleNode -- encode to\ntagged hasher --> MerkleHash
+    end
+    MerkleHash ---> MerkleNode
+    MerkleHash === Root
+    Leaf -- commit_id ----> MerkleHash
+```
+
+
+## Specific RGB consensus commitments
+
+Currently, RGB has three consensus commitments: schema, operation and bundle.
+Operation commitment for genesis has a second representation, named contract id,
+which uses reversed-byte encoding and a special string serialization, but is
+generated with the same procedure as the operation commitment.
+
+The commitment ids can be generated with either type-specific methods
+(`schema_id()` for schema, `bundle_id()` for state transition bundle and
+`id()` for any operation) or `CommitId::commit_id()` method, which must provide
+the equal result.
+
+Here are more details on each type of the commitments:
+
+| Commitment ID        | Produced by                          | Procedure                                                                                      | Tag URN suffix(1)             |
+|----------------------|--------------------------------------|------------------------------------------------------------------------------------------------|-------------------------------|
+| `SchemaID`           | `RootSchema`, `SubSchema`            | strict serialization                                                                           | `rgb:schema#2024-02-03`       |
+| `OpId`, `ContractId` | `Genesis`, `Transition`, `Extension` | nested commitments with concealing, merklization etc via intermediate `OpCommitment` structure | `rgb:operation#2024-02-03`    |
+| `BundleId`           | `TransitionBundle`                   | conceal and partial strict serialization                                                       | `rgb:bundle#2024-02-03`       |
+| `SecretSeal`         | `BlindSeal`                          | strict serialization                                                                           | `seals:secret#2024-02-03`     |
+| `ConcealedData`      | `RevealedData`                       | strict serialization                                                                           | `rgb:state-data#2024-02-12`   |
+| `ConcealedAttach`    | `RevealedAttach`                     | strict serialization                                                                           | `rgb:state-attach#2024-02-12` |
+
+(1): "URN suffix" is a part which follows "urn:lnp-bp:" prefix.
+
+The last three commitments coincide to be a concealed form of BP seals and RGB state.
+These commitments produced by either calling `commit_id` or `conceal` methods of
+revealed seal (`BlindSeal`) and state types (`RevealedData` and `RevealedAttach`).
+
+Additionally to these types there are two other commitment ids used internally
+by merklization and strict encoding procedures: `MerkleHash` (discussed in the
+Merklization section above) and `StrictHash` from `commit_verify` crate:
+
+| Commitment ID     | Tag URN suffix                                   |
+|-------------------|--------------------------------------------------|
+| `MerkleHash`      | `urn:ubideco:merkle:node#2024-01-31`             |
+| `StrictHash`      | `urn:ubideco:strict-types:value-hash#2024-02-10` |
+| `mpc::Commitment` | `urn:ubideco:mpc:commitment#2024-01-31`          |
+
+`StrictHash` can be produced as a result of serialization of any 
+strict-encodable data; for instance, it is used in compactifying collections 
+into a single hash field in the process of computing operation ids (described
+below).
+
+Finally, in `commit_verify::mpc`, multi-protocol commitment protocol 
+implementation, we have a type named `mpc::Commitment`, which is a commitment 
+to a root of the MPC tree (i.e. the tree's root `MerkleHash` is tag-hashed once
+again to produce the final commitment value).
+
+
+### Schema ID
+
+Schema id, represented by `SchemaId` data type, is produced from `Schema` type
+via strict serialization of all the schema data using 
+`urn:lnp-bp:rgb:schema#2024-02-03` hash tag. No conceal or merklization 
+procedures are applied; i.e. the commitment id is the same as hashing serialized
+schema with the given tag. The full description of how schema data are 
+serialized into the hasher can be found in [`Schema.vesper`](
+../stl/Schema.vesper) file, which is automatically generated from the RGB rust
+code.
+
+### Operation ID and Contract ID
+
+Operation id is represented by a `OpId` type and produced for `Genesis`, 
+`Transition` and `Extension` types via custom algorithm, which first creates a
+dedicated `OpCommitment` structure, and strict-serializes it to hasher, 
+initialized with `urn:lnp-bp:rgb:operation#2024-02-03` hash tag. 
+
+The `OpCommitment` by itself consists of a sub-commitments to blocks of the
+operation data, where each sub-commitment is created with a custom procedure.
+For instance, operation global state, inputs and assignments are merklized,
+such that a succinct proofs of some specific state or input inclusion in RGB
+operation can be produced and used in smart contracts. Additionally to that,
+assignments are concealed before the merklization, and range proofs are 
+removed from the commitment, such that an aggregation of the historical proofs
+can be applied without changing the operation ids. 
+
+To ensure succinctness, other types of collections, such as redeemed and 
+defined valencies and list of alternate layer 1 in genesis are not merklized 
+and strict-serialized producing `StrictHash`, which participates in the final 
+`OpCommitment` structure.
+
+```mermaid
+flowchart LR
+  subgraph "Common data"
+    Ffv --> OpCommitment
+    TypeCommitment --> OpCommitment
+    Metadata -- StrictHash --> OpCommitment
+    Globals -- Merklize --> OpCommitment
+    Inputs -- Merklize --> OpCommitment
+    Assignments -- "Conceal\n + Merklize" --> OpCommitment
+    Redeemed -- StrictHash --> OpCommitment
+    Valencies -- StrictHash --> OpCommitment
+  end
+
+  subgraph "Genesis"
+    schemaId --> BaseCommitment
+    testnet --> BaseCommitment
+    altLayers1 -- StrictHash --> BaseCommitment
+  end
+
+  subgraph "Transition"
+    tcid[contractId] --> TypeCommitment
+    transitionType --> TypeCommitment
+  end
+
+  subgraph "Extension"
+    ecid[contractId] --> TypeCommitment
+    extensionType --> TypeCommitment
+  end
+
+  BaseCommitment --> TypeCommitment
+
+  OpCommitment -- hash --> OpId
+  OpId -- "reverse bytes\n(genesis only)" --> ContractId
+```
+
+Additionally to `OpId`, genesis produces `ContractId`, which is made out of the
+genesis `OpId` by reversing byte order and using Base58 encoding.
+
+### Bundle ID
+
+Bundle id is a unique identifier of state transition bundle, directly used in
+constructing multi-protocol commitment tree. Bundle id commits to operation ids
+for the participating state transitions and maps of the witness transaction 
+input to the operation ids. For this purpose, the commitment is created by 
+strict-encoding `input_map` field of `TransitionBundle` into the hasher, 
+initialized with tag `urn:lnp-bp:rgb:bundle#2024-02-03`. Input map is serialized
+first as a 16-bit little-endian integer specifying the number of the items in
+the map, followed by the sequence of pairs of input number (32-bit LE value) 
+and `OpId` (32-bytes).
+
+```mermaid
+flowchart TD
+  subgraph Discarded
+      id((" "))
+  end
+
+  subgraph TransitionBundle
+    inputMap
+    knownTransitions
+  end
+    
+  inputMap -- encode \n hash --> BundleId
+  knownTransitions --x Discarded
+```
+
+
+[`commit_verify`]: https://docs.rs/commit_verify