> For the complete documentation index, see [llms.txt](/llms.txt).

# Secp256k1 private key

To retrieve the secp256k1 private key of the user, use `getPrivateKey` method. The method returns an EVM compatible private key which can be used to sign transactions on EVM compatible chains.

note

Web3Auth supports two widely used cryptographic curves, Secp256k1 and Ed25519, making it chain-agnostic and compatible with multiple blockchain networks. [Learn more about how to connect different blockchains](/embedded-wallets/connect-blockchain/).

Session behavior

- When `initialize()` completes and no active session exists, `getPrivateKey()` returns an **empty string** (`""`). Use this to check for an active session.
- After a successful `connectTo()`, `getPrivateKey()` returns the private key.
- If `useSFAKey = true` in `Web3AuthOptions`, this method returns the SFA core kit key instead of the standard secp256k1 key.
- `getPrivateKey()` throws `IllegalStateException` if the internal response is in an unexpected null state.

## Usage[​](#usage "Direct link to Usage")

```
val initializeCF = web3Auth.initialize()
initializeCF.whenComplete { _, error ->
    if (error == null) {
        val privateKey = web3Auth.getPrivateKey()
        if (privateKey.isNotEmpty()) {
            // Active session found, user is already logged in
        } else {
            // No active session, prompt user to log in
        }
    }
}

```