In the Substrate framework, how do you get the private key (secret key) from a Keypair?

Question

I have this code:

use schnorrkel;
use schnorrkel::{
    derive::{ChainCode, Derivation, CHAIN_CODE_LENGTH},
    signing_context, Keypair, MiniSecretKey, PublicKey, SecretKey,
};
use substrate_primitives::crypto::Pair as PairT;
use substrate_primitives::sr25519;
use substrate_primitives::sr25519::Pair;

fn main() {
    let keypair = sr25519::Pair::generate();
    let private_key = keypair.somehow_get_the_private_key_func();
}

I tried to use the SecretKey trait (imported at the beginning), but it says SecretKey is private, so the only way I am thinking of is to modify Substrate's sources to add a function that gives me the private key, but I don't want to do it by source code alteration.

What would be the way to go?

user_7482953 · Answer

What do you actually need to do? You shouldn't be getting a private key in the runtime at all.

If you want to sign something in your runtime, there are helper functions that will sign a message, if you just pass in the public key, with its corresponding private key.

https://substrate.dev/rustdocs/master/sp_io/crypto/fn.sr25519_sign.html testing: https://substrate.dev/rustdocs/master/sp_core/testing/struct.KeyStore.html

In the Substrate framework, how do you get the private key (secret key) from a Keypair?

1 Answers