[adrianvrj]

Summary

Starknet now works like Solana and Stellar: the key derives from the MasterDEK, recovery is off-chain (enclave or passkey PRF), and there is no on-chain device management. The account is the standard OpenZeppelin AccountUpgradeable v3.0.0 instead of the custom Cairo DeviceAccount.

• Key: HKDF(DEK, appSalt, "cavos-stark-starknet-v1") → grindKey (EIP-2645 rejection sampling) → stark key.
• Address: calculateContractAddressFromHash(pubKey, OZ_ACCOUNT_CLASS_HASH, [pubKey], 0), the OZ convention from the starknet.js guide. The Cavos paymaster deploys through UDC with unique=0, which yields the same address.
• Class hash: 0x01d1777d…02381 (OZ v3.0.0, Scarb 2.13.1 --release, audited in audits/2025-11-v3.0.0.pdf). It is declared on mainnet and Sepolia, and its ABI matches v4.0.1's: constructor (public_key), SRC-9 V2, upgrade. It is pinned forever, because the address derives from it. Later changes go through the account's upgrade, which keeps the address. That is also the path to post-quantum (OZ Falcon-512) later.
• Deploy: lazy, on the first sponsored execute (executePaymasterTransaction with deploymentData), same as before.
• signMessage: SNIP-12 revision 1 typed data, verifiable with the account's is_valid_signature. Returns curve: "stark" plus the typedData.
• Guard: execute/signTransaction refuse set_public_key on the account itself, by name or selector. A rotated key would no longer be controlled by the DEK.
• Vault: the Starknet branch derives through resolveNativeStarknet, like Solana. signStarknetMessage is removed; messages go through signStarknetTypedData.
• Removed:
  • the Starknet adapter and device signer;
  • the WebCrypto and passkey P-256 signers, and the WebAuthn and P-256 signature helpers;
  • SocialRecoveryCoordinator, HttpRecoveryClient, BackupSigner, identity.ts;
  • the device approval and revoke pages;
  • React addSigner, removeSigner, listDevices, resendDeviceApproval, enrollPasskey, and Cavos.recover;
  • dead throwing stubs on CavosSolana.
• The recovery-phrase UI in the auth modal now shows only on Stellar, the one chain where recovery codes work.

Released as 0.4.2. This is a breaking change shipped as a patch, so any app on ^0.4.x picks it up on its next install.

Trade-offs

• WebCrypto cannot hold a stark key. Outside the vault, the key is re-derived into memory from the device-wrapped DEK. The DEK at rest stays protected by the non-extractable device key. On React Native the Starknet key is no longer hardware-backed.

Rollout notes

• Vault protocol: the Starknet vault protocol changed. cavos-web serves the vault host from the npm package (lib/vault/copyAssets.mjs), so it must be redeployed with 0.4.2 before apps use 0.4.2 on Starknet. Any cavos-web redeploy picks up 0.4.2 through ^0.4.1.
• Dead backend code: the cavos-web /api/devices/* routes and the enclave's ChainAuthorization::Starknet are now unused. Their cleanup is a separate change.

Test plan

• tsc --noEmit clean.
• jest: 57 suites, 381 passed, 2 skipped.
• New tests:
  • pinned derivation vector (seed → key → address);
  • OZ address formula;
  • deploymentData shape on the first execute;
  • status transitions;
  • the key-rotation guard (name, selector, zero padding);
  • SNIP-12 signature verified against the typed-data hash;
  • the vault host Starknet branch.
• Not yet verified on-chain: the sponsored OZ deploy through the Cavos paymaster, and is_valid_signature on a deployed account.