Encrypt a private key¶

Before saving a local private key, encrypt it with a passphrase. The resulting ncryptsec1… string uses the NIP-49 format and can be restored later:

String encrypted = privateKey.asNcryptsec(passphrase).await();
NostrPrivateKey restored = NostrPrivateKey
    .fromNcryptsec(encrypted, passphrase).await();

If you need to choose the derivation work factor or memory limit, use the Nip49 helpers directly. You can estimate the memory needed with Nip49.getApproximatedMemoryRequirement(logn) before starting.

Decryption rejects oversized or malformed encrypted-key input before deriving a key. Keep the derivation memory limit appropriate to the device running your app.

Choose a strong passphrase and protect the stored file. Close the restored private key after use. Avoid making plaintext String copies: closing the key cannot erase those copies. See key storage for the surrounding account lifecycle.