Version: 0.13

MASM Changes

MASM syntax has been modernized. Replace dotted keywords (const., export., use.) with spaced forms.

Quick Fix

src/contract.masm
# Before
const.MY_CONSTANT=42
use.miden::account
export.my_procedure

# After
const MY_CONSTANT=42
use miden::account
export my_procedure

Syntax Modernization

Replace dotted keywords with spaced forms:

Constants

src/contract.masm
- const.MY_CONSTANT=42
+ const MY_CONSTANT=42

Exports

src/contract.masm
- export.my_procedure
+ export my_procedure
    # procedure body
- end
+ end

Imports

src/contract.masm
- use.miden::account
- use.miden::note

+ use miden::account
+ use miden::note

Re-exports

src/contract.masm
- export.miden::account::get_id
+ pub use miden::account::get_id

Use sed to batch-update MASM files:

# Update constants
sed -i 's/const\./const /g' *.masm

# Update exports
sed -i 's/export\./export /g' *.masm

# Update imports
sed -i 's/use\./use /g' *.masm

Named Storage Slots

Storage access is now name-based, not index-based. Use word("...") to derive slot IDs from names.

In v0.13, account storage slots are identified by name rather than numeric index. In MASM, the word("...") syntax computes a deterministic slot ID from a slot name string:

src/contract.masm
- # Before (v0.12): index-based storage access
- const.BALANCE_SLOT=0
- push.BALANCE_SLOT
- exec.account::get_item

+ # After (v0.13): name-based storage access
+ use miden::protocol::active_account
+ const BALANCE_SLOT = word("my_project::my_component::balance")
+ push.BALANCE_SLOT[0..2]
+ exec.active_account::get_item

Key changes:

Define slot constants using word("slot_name") instead of integer indices
The word() function hashes the name string to produce a Word (4 field elements)
Use [0..2] slice notation to extract the slot ID (first 2 elements) for kernel procedures like get_item and set_item
Slot names should follow the project::component::slot naming convention to avoid collisions

For more details on storage slot naming conventions, see Account Storage. For the full list of storage procedures, see the Protocol Library Reference.

Cryptography Updates

Falcon Signature Rename

Rename RpoFalcon512 to Falcon512Rpo throughout codebase:

src/auth.masm
- use.miden::contracts::auth::basic::auth_tx_rpo_falcon512
+ use miden::contracts::auth::basic::auth_tx_falcon512_rpo

ECDSA Procedures

ECDSA procedures moved to new namespace:

src/crypto.masm
- use.miden::crypto::dsa::ecdsa
- exec.ecdsa::verify_k256

+ use miden::core::crypto::dsa::ecdsa_k256_keccak
+ exec.ecdsa_k256_keccak::verify

RPO Hash Renames

The RPO module was renamed from rpo to rpo256, and several procedures were renamed to standardize naming across all hash modules:

src/hash.masm
- use.std::crypto::hashes::rpo
+ use miden::core::crypto::hashes::rpo256

- exec.rpo::hash_memory
+ exec.rpo256::hash_elements

- exec.rpo::hash_memory_words
+ exec.rpo256::hash_words

- exec.rpo::hash_memory_double_words
+ exec.rpo256::hash_double_words

- exec.rpo::hash_memory_with_state
+ exec.rpo256::hash_elements_with_state

- exec.rpo::hash_1to1
+ exec.rpo256::hash

- exec.rpo::hash_2to1
+ exec.rpo256::merge

Complete MASM Migration Example

Before:

src/contract.masm (before)
use.miden::account
use.std::crypto::hashes::rpo

const.BALANCE_SLOT=0

export.get_balance
    push.BALANCE_SLOT
    exec.account::get_item
end

export.transfer
    exec.rpo::hash_memory_words
    # ... rest of procedure
end

After:

src/contract.masm (after)
use miden::protocol::active_account
use miden::core::crypto::hashes::rpo256

const BALANCE_SLOT = word("my_project::my_component::balance")

export get_balance
    push.BALANCE_SLOT[0..2]
    exec.active_account::get_item
end

export transfer
    exec.rpo256::hash_words
    # ... rest of procedure
end

Migration Steps

Find all .masm files in your project
Replace const. with const (space instead of dot)
Replace export. with export (space instead of dot)
Replace use. with use (space instead of dot)
Replace export.<path> re-exports with pub use <path>
Update std:: namespace to miden::core::
Replace numeric storage slot constants with word("...") named slots
Update get_item/set_item calls to use [0..2] slice for slot IDs
Rename RpoFalcon512 to Falcon512Rpo
Update ECDSA procedure paths
Rename RPO module rpo to rpo256
Rename hash_memory to hash_elements, hash_memory_words to hash_words, hash_memory_double_words to hash_double_words, hash_memory_with_state to hash_elements_with_state
Rename hash_1to1 to hash, hash_2to1 to merge

Common Errors

Error	Cause	Fix
`unexpected token '.'`	Old syntax	Use space: `const X` not `const.X`
`module 'std' not found`	Namespace changed	Use `miden::core::`
`procedure 'auth_tx_rpo_falcon512' not found`	Renamed	Use `auth_tx_falcon512_rpo`
`procedure 'hash_memory' not found`	Renamed	Use `hash_elements` (module `rpo256`)
`procedure 'hash_memory_words' not found`	Renamed	Use `hash_words` (module `rpo256`)
`procedure 'hash_1to1' not found`	Renamed	Use `hash` (module `rpo256`)
`procedure 'hash_2to1' not found`	Renamed	Use `merge` (module `rpo256`)
`module 'rpo' not found`	Renamed	Use `rpo256`
`get_item` returns unexpected values	Using integer index instead of slot ID	Use `word("...")` and `[0..2]` slice

Quick Fix​

Syntax Modernization​

Constants​

Exports​

Imports​

Re-exports​

Named Storage Slots​

Cryptography Updates​

Falcon Signature Rename​

ECDSA Procedures​

RPO Hash Renames​

Complete MASM Migration Example​

Migration Steps​

Common Errors​