# Submission and verification

Once you have registered your application's verifying key(s) you are ready to submit application proofs to NEBRA UPA. In this section you will learn how to submit and verify proofs using our SDK.

## Steps to submit and verify proofs

Proofs are submitted to UPA on-chain by calling the `submit`

function in the NEBRA UPA contracts.

Each submission can contain one or more proofs. For convenience and type-safety, we recommend that you use our SDK to submit proofs instead of calling this function directly.

### Step 1: Export proof data

#### SnarkJS

Let `proofData`

be the output of snarkjs' `fullProve`

function, i.e.

You may save the json serialization of `proofData`

into a file `proof.upa.json`

if you intend to submit the proof with the `upa`

tool. This file will contain both the proof and the public inputs and is already UPA-compatible.

Alternatively, if you want to submit via the typescript sdk, you can easily extract the UPA-compatible proof and inputs from `proofData`

:

#### Gnark

You can modify your gnark circuit code to export the proof and the inputs as follows:

If you intend to submit the proof with the `upa`

tool, you may generate a UPA-compatible proof data file with the following command

Alternatively, if you want to submit via the typescript sdk, you can convert the gnark proofs and inputs to the UPA-compatible format as follows

where `gnarkProof`

and `gnarkInputs`

can be obtained from the `gnark_proof.json`

and `gnark_inputs.json`

files, respectively. For example

#### Note on gnark proofs

For gnark proofs with a LegoSNARK commitment point, the UPA only supports those which have been generated with `keccak256`

as the hash to field function. In other words, you must run the prover with the following options:

Note `gnark`

's default is the hash function RFC9380, which is not currently supported by NEBRA's UPA.

### Step 2: Prepare proof data

Each proof is submitted along with its corresponding Circuit Id and public inputs as a `CircuitIdProofsAndInputs.`

Prepare an array `CircuitIdProofsAndInputs[]`

of the proofs you will submit.

### Step 3: Submit proofs

Using your `UpaClient`

(see setup), submit your array `CircuitIdProofsAndInputs[]`

.

Be sure to keep the returned `submissionHandle`

as it contains information used by your application contract to check whether the proof has been verified by NEBRA UPA. It contains a `Submission`

object that stores the *proof Ids** *for each submitted proof and a *submission Id* for the entire submission. See Single and multi-proof submissions for more details.

#### Fee estimation (optional)

NEBRA UPA charges a nominal fee for each proof submission.** **Your `UpaClient`

can estimate this fee.

This fee amount `value`

can then be passed as a `PayableOverrides`

option into `upaClient.submitProofs`

. If no `value`

is specified then the fee is computed automatically.

#### Proof submission via the `upa`

tool

`upa`

tool If you have a json file with UPA-compatible proof data such as `proof.upa.json`

generated in the previous step, you can also submit proofs with the following command:

The argument `-i`

above is optional and produces an output file with the proof id. Similarly, for multi-proof submissions:

where `proofs.upa.json`

consists an array of objects with three UPA-compatible components: verifying key, proof and a public inputs array. The arguments `-i`

and `-s`

are optional and produce output files with the proof ids and the submission data, respectively.

### Step 4: Wait for proofs to be verified on NEBRA UPA

Wait for NEBRA UPA to verify your submission by awaiting `waitForSubmissionVerified`

from your `UpaClient.`

Once your submission has been verified, you can send a request to your application contract with inputs corresponding to your submission. This request uses the same inputs as before, but you will no longer need to pass in a proof when using NEBRA UPA. Your application contract will use NEBRA UPA to check the verification status of these inputs before executing the request.

### Step 5: Application contract checks verification status

Your app smart contract will call `isVerified`

from the NEBRA UPA contracts to check whether a proof has been verified or not.

For single-proof submissions, your smart contract calls `isVerified`

as follows.

For multi-proof submissions, your application contract will also need to provide a `ProofReference`

to identify a specific proof in the submission (see Proof references).

If you used our typescript SDK for a multi-proof submission, your `SubmissionHandle`

can compute this proof reference which can then be passed to your application contract as part of your request.

## What is a Proof Id?

## Single and multi-proof submissions

A submission's proofs are either all accepted if all of them are valid, or they are all rejected if any proof is invalid.

An aggregated batch can contain proofs from different submissions.

#### Proof references

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