Crate ic_certified_map

This package provides a map backed by a Merkle tree that can be used by Internet Computer canisters to implement certified queries.

You can certify your data by using the RbTree type as a map of known names to the values you want certified. After you record its root_hash into your canister’s certified data, query calls can access a data certificate proving that the IC certified the hash, under the path /canister/<canister id>/certified_data. By providing this certificate, as well as a witness that the value exists in the hash, you can then prove to the caller that the IC certified the data.

Example

thread_local! {
    static COUNTER: Cell<i32> = Cell::new(0);
    static TREE: RefCell<RbTree<&'static str, Hash>> = RefCell::new(RbTree::new());
}

#[update]
fn inc() {
    let count = COUNTER.with(|counter| {
        let count = counter.get() + 1;
        counter.set(count);
        count
    });
    TREE.with(|tree| {
        let mut tree = tree.borrow_mut();
        tree.insert("counter", leaf_hash(&count.to_be_bytes()));
        ic_cdk::api::set_certified_data(&tree.root_hash());
    })
}

#[derive(CandidType)]
struct CertifiedCounter {
    count: i32,
    certificate: Vec<u8>,
    witness: Vec<u8>,
}

#[query]
fn get() -> CertifiedCounter {
    let certificate = ic_cdk::api::data_certificate().expect("No data certificate available");
    let witness = TREE.with(|tree| {
        let tree = tree.borrow();
        let mut witness = vec![];
        let mut witness_serializer = serde_cbor::Serializer::new(&mut witness);
        witness_serializer.self_describe();
        tree.witness(b"counter").serialize(&mut witness_serializer).unwrap();
        witness
    });
    let count = COUNTER.with(|counter| counter.get());
    CertifiedCounter {
        count,
        certificate,
        witness,
    }
}

Structs

• Iter
  Iterator over a RbTree.
• RbTree
  Implements mutable left-leaning red-black trees as defined in https://www.cs.princeton.edu/~rs/talks/LLRB/LLRB.pdf

Enums

• HashTree
  HashTree as defined in the interfaces spec.

Traits

• AsHashTree
  Types that can be converted into a HashTree.

Functions

• fork
  Shorthand for HashTree::Fork.
• fork_hash
  Identifiably hashes a fork in the branch. Used for hashing HashTree::Fork.
• labeled
  Shorthand for HashTree::Labeled.
• labeled_hash
  Identifiably hashes a label for this branch. Used for hashing HashTree::Labeled.
• leaf_hash
  Identifiably hashes a leaf node’s data. Used for hashing HashTree::Leaf.

Type Definitions

• Hash
  SHA-256 hash bytes.