How can a WebAuthn passkey authorize an actual on-chain transaction?

The transaction's own fields - network, sender, recipient, asset, amount, fee, fee collector, and a replay-protection nonce - are assembled into a canonical string, hashed, and used as the WebAuthn challenge. When the user's device signs that challenge with its passkey, the resulting P-256 assertion is a direct cryptographic authorization of that exact transaction, not merely a login event.

Who verifies the passkey signature?

The blockchain validator node itself, deterministically, using only data already contained in the transaction and the account's registered public key - no call to an external authentication service, identity provider, or FIDO server is required or possible during verification.

Can a relayer alter the fee or redirect it to another destination?

No. The fee amount and fee-collector identifier are both part of the canonical string that was hashed into the signed challenge, so changing either value after the user signs invalidates the signature and the validator rejects the transaction.

Does the user need to manage a seed phrase or private key?

No. Authorization runs through the device's platform authenticator (passkey) rather than an exported private key or mnemonic seed phrase that the user must store and protect.

WebAuthn Passkeys as Validator-Level L1 Transaction Authorization

Executive Summary

Almost every consumer-facing product that uses WebAuthn passkeys today uses them for one purpose: logging into a web session. The passkey unlocks an app, and the app - not the passkey - is what actually authorizes a transaction using a separately-held private key. JIL Sovereign's ledger service instead treats the raw WebAuthn P-256 assertion as the transaction-authorization primitive itself: the assertion is verified directly by validator node code, and the thing being signed is a canonical encoding of the transaction's own fields, not a generic login challenge.

Because the verification logic depends only on data already present in the transaction and the account's registered public key, it is deterministic and safe to execute inside consensus-critical validator code - every validator reaches the same accept/reject answer without calling out to an authentication service, an identity provider, or Apple/Google/Microsoft's own servers.

Core Innovation: A consumer WebAuthn passkey assertion, verified deterministically by validator node code against a challenge that encodes the transaction's own network, parties, asset, amount, fee, and fee collector - so the signature itself is the on-chain authorization, and a relayer cannot alter the fee or its destination without invalidating it.

Problem Statement

Self-custody blockchain wallets have historically forced a choice between security and accessibility: a raw private key or BIP-39 seed phrase gives full self-custody but is a single point of catastrophic, unrecoverable loss for a mainstream user, while custodial wallets remove that burden by giving up self-custody entirely. Passkeys solve the usability half of this problem for web login, but most blockchain integrations of passkeys stop at the login boundary - the passkey unlocks a session, and a conventional private key, held somewhere else in the stack, is what actually signs the transaction. That leaves the private-key-loss problem exactly where it was.

Transaction fields cryptographically bound into the signed challenge

Minimum byte length enforced on authenticatorData before parsing

Raw private keys or seed phrases held by the user

Why Passkey-Gated Wallets Fall Short

Passkey-gated session login: the passkey authenticates a user into an app; a separately-stored private key still performs the actual transaction signature.
Hardware wallets with PIN entry: device-bound and phishing-resistant, but not natively verifiable by a validator without an external attestation service.
Custodial exchange accounts: remove the seed-phrase burden entirely by taking custody, the opposite tradeoff.
Generic FIDO2 authentication middleware: designed for HTTP session authentication, not for producing a signature a consensus-critical validator can verify deterministically against transaction-specific fields.

Technical Architecture

The Canonical Transaction Challenge

Before a transaction is signed, the wallet client and the validator both independently compute the same canonical string from the transaction's own fields: network identifier, sender, recipient, asset, amount, fee, fee collector, and nonce, joined with a fixed delimiter. That string is hashed (SHA-256) and the resulting digest, base64url-encoded, becomes the WebAuthn challenge value presented to the authenticator. Binding fee and fee collector into the challenge means a relayer submitting the transaction on the user's behalf cannot inflate the fee or redirect it to a different destination - either change produces a different challenge and invalidates the signature.

Deterministic Validator-Side Verification

Check	What Is Verified
authenticatorData length	Rejected outright if shorter than 37 bytes, before any further parsing
rpIdHash	First 32 bytes of authenticatorData must equal SHA-256 of the expected relying-party identifier
User-presence flag	Must be set in the authenticatorData flags byte
User-verification flag (optional)	When required, must also be set in the flags byte
clientDataJSON.type	Must equal `webauthn.get`
clientDataJSON.challenge	Must equal the transaction-derived challenge computed independently by the validator
Signature	P-256 ECDSA signature over authenticatorData \|\| SHA-256(clientDataJSON), verified against the account's registered public key

All seven checks run against data already carried in the assertion and the transaction; none require a network call. That determinism is what allows the check to run safely inside validator node code rather than an off-chain authentication tier - every validator computing the same expected challenge and the same rpIdHash will reach the same verification result.

Fee and Relayer Tamper Binding

Many account-abstraction and meta-transaction designs let a relayer submit a transaction on the user's behalf while charging a fee for doing so - and a common weakness is that the fee amount or destination is decided by the relayer at submission time, outside anything the user actually signed. Because fee and fee_collector are explicit fields in JIL Sovereign's canonical challenge string, they are locked at the moment of signing: an empty fee collector produces one canonical string, a non-empty one produces a different string entirely, and any relayer-side modification after signing changes the digest the validator recomputes, causing signature verification to fail. The user's signature is authorization for one specific fee, to one specific collector - not a blank check to the relaying infrastructure.

Prior Art Differentiation

Approach	What the Passkey Actually Authorizes	Verified By	Fee/Destination Tamper-Bound?
Passkey-gated web session	App login only	Application backend / identity provider	No
Hardware wallet + PIN	Transaction signing, device-local	Device firmware	Depends on client implementation
Raw private-key / seed-phrase wallet	Transaction signing	Client software	Depends on client implementation
JIL Sovereign passkey-as-L1-authorization	The exact transaction (network/parties/asset/amount/fee/fee-collector/nonce)	Validator node, deterministically, in-consensus	Yes - fee and collector are hashed into the signed challenge

Patent Claim

Independent Claim 46: A computer-implemented method for validator-level transaction authorization comprising: constructing a canonical challenge string that concatenates a network identifier, a source account identifier, a destination account identifier, an asset identifier, a transfer amount, a fee amount, and a fee-collector identifier, together with a replay-protection nonce; hashing the canonical challenge string to produce a WebAuthn challenge value; receiving, at a blockchain validator node, a WebAuthn P-256 assertion comprising authenticator data, a client-data JSON structure, and a signature; verifying, deterministically and without reliance on any external authentication service, that a relying-party-identifier hash embedded in the authenticator data matches an expected value, that a user-presence flag is set, that the client-data JSON's embedded challenge matches the hashed canonical challenge value, and that the signature validates against a registered public key over the concatenation of the authenticator data and a hash of the client-data JSON; and committing the transaction to the ledger only upon successful verification, such that a relaying party cannot alter the fee amount or the fee-collector identifier without invalidating the signature.