Skip to main content
Version: 0.16 (unstable)

Hashing, SMT & Crypto Changes

SMT leaf hashing now mixes a Poseidon2 leaf-domain separator into the capacity word, and miden-crypto bumped to 0.25. These are digest-changing: persisted SMT roots, leaf digests, and PartialSmt values from earlier versions do not round-trip.

SMT leaf hashing switched to Poseidon2 domain separation​

Summary​

The core library's Sparse Merkle Tree leaf hashing (miden::core collections::smt) now mixes a leaf‑domain separator into the Poseidon2 capacity word, so MASM‑side leaf digests match SmtLeaf::hash() in miden-crypto. Leaf preimages are hashed with poseidon2::merge_in_domain using LEAF_DOMAIN = 0x13af. This is a digest‑changing change: any SMT leaf digest, SMT root, or advice‑map key derived from MASM‑side leaf hashing under 0.22 will not reproduce under 0.23. It pairs with the miden-crypto 0.25 bump.

Affected Code​

MASM (core‑lib collections::smt, simplified):

- exec.poseidon2::merge assert_eqw
+ push.LEAF_DOMAIN exec.poseidon2::merge_in_domain assert_eqw

The per‑leaf cycle cost also changed (the pair_count coefficient went from 3 to 6), so any hard‑coded cycle‑count expectations around smt::get / smt::set need updating.

Migration Steps​

  1. Re‑derive every persisted SMT root, leaf digest, and advice‑map key computed from a MASM‑side SMT leaf hash under 0.22.
  2. If you compute SMT leaf digests in Rust via miden-crypto, upgrade to 0.25 so both sides agree.
  3. Discard cached proofs / transaction artifacts whose witnesses depend on the old leaf hashing.

miden-crypto 0.25 downstream renames​

Summary​

Bumping to miden-crypto 0.25 (and miden-vm 0.23) surfaces several renames in code that builds against the protocol crates directly:

  • Felt::new(n) call sites that want the previous (non‑reducing) behaviour are now Felt::new_unchecked(n) (Felt::new now reduces modulo the field).
  • The ECDSA secret key type ecdsa_k256_keccak::SecretKey is renamed SigningKey; the EdDSA/X25519 key eddsa_25519_sha512::SecretKey is KeyExchangeKey. Falcon's falcon512_poseidon2::SecretKey is unchanged.
  • The kernel's EMPTY_SMT_ROOT constant was recomputed for the Plonky3‑aligned Poseidon2 and the domain‑separated SmtLeaf::hash — any hard‑coded SMT‑root literal changes.
  • In kernel/standards MASM, the immediate form of adv_push was dropped and cross‑module‑referenced MASM constants/procedures must be marked pub.

Affected Code​

- let f = Felt::new(value);
- use miden_protocol::crypto::dsa::ecdsa_k256_keccak::SecretKey;
- use miden_protocol::crypto::dsa::eddsa_25519_sha512::SecretKey as EdSecretKey;
+ let f = Felt::new_unchecked(value);
+ use miden_protocol::crypto::dsa::ecdsa_k256_keccak::SigningKey;
+ use miden_protocol::crypto::dsa::eddsa_25519_sha512::KeyExchangeKey;

Migration Steps​

  1. Replace Felt::new(...) with Felt::new_unchecked(...) where you relied on the non‑reducing constructor.
  2. Rename ecdsa_k256_keccak::SecretKey → SigningKey and eddsa_25519_sha512::SecretKey → KeyExchangeKey.
  3. Mark any cross‑module‑referenced MASM constants/procedures pub, and regenerate hard‑coded EMPTY_SMT_ROOT / SMT‑root literals.

PartialSmt serialization changed​

Summary​

In miden-crypto 0.25 the serialized byte layout of PartialSmt changed. Old serialized PartialSmt values are not compatible with 0.25 and will not deserialize correctly.

Migration Steps​

  1. Discard any PartialSmt values serialized under an earlier miden-crypto.
  2. Rebuild them from current state, or re‑fetch them under 0.25.

Custom LargeSmt storage backends: reads move to SmtStorageReader​

Summary​

Custom LargeSmt storage backends need a small trait update: reads moved to a dedicated SmtStorageReader. Writable storage still implements SmtStorage, but now also sets an associated type Reader and returns a point‑in‑time reader via reader(). Read operations go through SmtStorageReader rather than the writable SmtStorage directly.

Migration Steps​

  1. Keep your writable backend implementing SmtStorage, and add the associated type Reader plus a reader() method that returns a point‑in‑time SmtStorageReader.
  2. Move read operations onto the SmtStorageReader returned by reader().

Direct miden-crypto 0.24 API breaks​

Summary​

For the rare consumers that depend on miden-crypto directly, the 0.24 step carries a few additional API breaks:

  • The WORD_SIZE, WORD_SIZE_FELTS, and WORD_SIZE_BYTES constants moved to Word::NUM_ELEMENTS / Word::SERIALIZED_SIZE.
  • LexicographicWord is now just Word.
  • Felt no longer derefs.
  • Custom multi‑AIR prover/verifier code must handle StarkProof log trace heights and air_order.

Migration Steps​

  1. Replace WORD_SIZE / WORD_SIZE_FELTS with Word::NUM_ELEMENTS and WORD_SIZE_BYTES with Word::SERIALIZED_SIZE.
  2. Replace LexicographicWord with Word.
  3. Remove any reliance on Felt's Deref; access the inner value explicitly.
  4. If you maintain custom multi‑AIR prover/verifier code, update it to handle StarkProof log trace heights and air_order.