FHEVM Files

What's Changed

• Context-Aware Decryptions (#2143)

A new "KMS context" system adds epoch IDs and context state to decryption operations. KMSVerifier now tracks context IDs, and decryption requests carry context-aware extraData. The kms-connector validates context state via a new kms_context DB table and ethereum listener.

• Simple ACL — MultichainACL Removed (#2072)

The entire MultichainACL contract suite is removed from gateway-contracts. isUserDecryptionReady and isDelegatedUserDecryptionReady had unused parameters removed. The Arbitrum expiration-date-before-one-hour constraint is replaced by a simpler expirationDate > block.timestamp check. A backward-compatibility overload for the old isUserDecryptionReady signature is provided (#2137).

• Per-Block HCU Metering (#2004)

New HCULimit contract provides configurable per-block, per-transaction, and per-transaction-depth Homomorphic Compute Unit limits. Includes a whitelist mechanism for privileged callers to bypass block limits.

• Ciphertext Re-Randomisation (#1952, [#2073])

Ciphertext inputs are now re-randomised per FHE operation using a deterministic seed derived from input ciphertexts and operator, enabling coprocessor consensus.

• Coprocessor State Revert (#2122)

New revert_coprocessor_db_state.sql script that can revert a coprocessor to a previous block number, packaged in the db-migration Docker image.

• Gateway Drift Detection (#2096)

Opt-in ciphertext drift detection in the gateway listener, comparing local digests against on-chain consensus. Detection-only (no auto-recovery). Enable via --ciphertext-commits-address.

• KMS-Connector: eth_getLogs Event Listening (#2197)

KMS connector switches from subscription-based to eth_getLogs-based event listening with batch DB insertion.

• Contract Upgrade Version Check CI (#2112)

New CI workflow that enforces bumping REINITIALIZER_VERSION and version constants when contract bytecode changes.

• Library-Solidity Enhancements

• FHE.fromExternal now returns a trivial-encrypt of 0 for uninitialized handles instead of reverting (#1969)

• New FHE.isPublicDecryptionResultValid view function for on-chain decryption signature validation (#1987)
• ECDSA.sol renamed to FhevmECDSA.sol to fix naming conflicts (#2007)

Breaking Changes

Gateway Contracts

• MultichainACL contracts deleted — MultichainACL.sol, MultichainACLChecks.sol, and IMultichainACL.sol are removed entirely.
• isUserDecryptionReady signature changed — the address userAddress parameter was removed. Old signature preserved via backward-compat overload but is deprecated.
• Decryption contract upgraded for context-aware decryption and removed MultichainACL dependency.

Host Contracts

• Handle hashing includes domain separator + prev block hash — FHEVMExecutor now prepends COMPUTATION_DOMAIN_SEPARATOR ("FHE_comp") and appends blockhash(block.number-1) + block.timestamp.
• New HCULimit contract required — FHEVMExecutor REINITIALIZER_VERSION bumped to 3. Initialization requires hcuCapPerBlock, maxHCUDepthPerTx, and maxHCUPerTx parameters.
• ACL REINITIALIZER_VERSION bumped to 4 — ExpirationDateBeforeOneHour error replaced by ExpirationDateInThePast. Validation now only checks expirationDate > block.timestamp.
• KMSVerifier upgraded for context-aware decryption with epoch/context support.

Library Solidity

• ECDSA.sol renamed to FhevmECDSA.sol — import path changed from cryptography/ECDSA.sol to cryptography/FhevmECDSA.sol, library renamed from ECDSA to FhevmECDSA.

Coprocessor

• Tenants table removed from DB
• Legacy tfhe-worker gRPC endpoint removed
• tfhe-rs updated to 1.5.4