How to access and sign messages with keys from SessionKeys Keystore such as Aura?

Question

I would like to sign and gossip messages in an offchain service and leverage keys from the keystore used by the SessionKeys such as the Aura/Grandpa/etc. key. Our current strategy requires us to create an independent sr25519 key. Instead, we'd like to use an existing key so we can cross-reference signatures within the authority set.

What is the proper way to access the keys in this keystore?

Answer 1

In order to fetch the keys for a specific KEY_TYPE such as AURA you just need to use that keystore and pass in the respective KeyType w/ sr25519 / ecdsa / ed25519.

pub fn sr25519_public_keys(&self) -> Result<Vec<sr25519::Public>, error::Error> {
    let store: SyncCryptoStorePtr = self.0.clone().ok_or_else(|| error::Error::Keystore("no Keystore".into()))?;

    let pk: Vec<sr25519::Public> = SyncCryptoStore::sr25519_public_keys(&*store, AURA)
        .iter()
        .map(|k| sr25519::Public::from(k.clone()))
        .collect();

    Ok(pk)
}