Error to_affine_exn: Got identity when using public key retrieved from on-chain state

[garethtdavies]

I am using an on-chain public key variable in a zkApp for use in signature verification.

The public key is stored onchain and retrieved via let oraclePublicKey = this.oraclePublicKey.get();

However, when using oraclePublicKey it errors with:

/workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:7565
         throw err;

Error: to_affine_exn: Got identity
    at failwith (/workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:75528:50)
    at to_affine_exn (/workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:160233:36)
    at caml_call1 (/workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:7610:28)
    at scale$3 (/workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:337731:34)
    at /workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:420296:49
    at caml_call_gen (/workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:2081:17)
    at Object.scale (/workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/_node_bindings/snarky_js_node.bc.cjs:3651:16)
    at Signature.verify (file:///workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/lib/signature.js:126:23)
    at DelegationOracle.verify (file:///workspace/zkAppPool/oracle/build/src/DelegationOracleVerifier.js:46:42)
    at file:///workspace/zkAppPool/oracle/node_modules/snarkyjs/dist/node/lib/zkapp.js:152:32

If I simply override the oraclePublicKey with the following, it works just fine:

oraclePublicKey = PublicKey.fromBase58("B62qphyUJg3TjMKi74T2rF8Yer5rQjBr1UyEG7Wg9XEYAHjaSiSqFv1");

Code example here, with the above hack: https://github.com/garethtdavies/zkAppPool/blob/5176a050c469ebab978fcf9631c7ac6bfd590970/oracle/src/DelegationOracleVerifier.ts#L44

[mitschabaude]

Could it be that the public key is not initialized yet, so it's all zeroes? That's what the error message sounds like

[garethtdavies]

Do you mean it's not on-chain yet? It is stored in this account: B62qmLWZfcbqrQPMky44w6K6Myj9aydbHKE5fG2N6wrXxFbkfEUWdRM

You can see there the fields are 13117991216867267972578094433946611068215850158296483053051446309883779846074 and 0 . Manually decoding that via https://github.com/garethtdavies/zkAppPool/blob/main/oracle/src/debug-events.ts gives B62qphyUJg3TjMKi74T2rF8Yer5rQjBr1UyEG7Wg9XEYAHjaSiSqFv1 as expected.

Query to get on-chain state:

{
  account(publicKey: "B62qmLWZfcbqrQPMky44w6K6Myj9aydbHKE5fG2N6wrXxFbkfEUWdRM") {
    publicKey
    zkappState
  }
}

[mitschabaude]

I understand the error now - it's because of running stuff multiple times, the first one with fake values. We should address this soon

[mitschabaude]

So the goal would be to run it the first time in an environment where assertions don't throw

[mitschabaude]

@garethtdavies you could use the following workaround for now:

You can pass in the oraclePublicKey as an additional parameter to your method, to avoid .get() which gives you the wrong result. Then, to check that it matches the on-chain one, you can do this.oraclePublicKey.assertEquals(oraclePublicKey); as before.

So this would be the diff in pseudo code

+ // oraclePublicKey gets passed in as argument
- let oraclePublicKey = this.oraclePublicKey.get();
this.oraclePublicKey.assertEquals(oraclePublicKey);

[mitschabaude]

Oh! An even simpler workaround would be to warm the cache before doing the transaction:

await Mina.fetchAccount(zkAppAddress);

let tx = await Mina.transaction(...)