Keystore

An encrypted-on-disk container for a 32-byte private key, using AES-256-GCM with PBKDF2-HMAC-SHA256 key derivation.

Setup

Keystore does not need to be constructed directly — both static methods do the work. Reach for it through Keystore::from_file (load) or Keystore::write_to_file (save):

use {
    anyhow::Result,
    dango_sdk::{Keystore, Secp256k1, Secret},
};
 
fn save() -> Result<()> {
    let secret = Secp256k1::new_random();
    Keystore::write_to_file(&secret, "./key.json", "hunter2")?;
    Ok(())
}
 
fn load() -> Result<Secp256k1> {
    let bytes = Keystore::from_file("./key.json", "hunter2")?;
    Secp256k1::from_bytes(bytes)
}

#[grug::derive(Serde)]
pub struct Keystore {
    pub pk:         ByteArray<33>,
    pub salt:       ByteArray<16>,
    pub nonce:      ByteArray<12>,
    pub ciphertext: Binary,
}

Configuration

Keystore itself has no options. The KDF parameters are fixed:

PBKDF2-HMAC-SHA256
600 000 iterations
16-byte salt (OsRng)
12-byte AES-GCM nonce (OsRng)
AES-256-GCM cipher

Methods

Method	Description
`from_file`	Read and decrypt a keystore file. Returns the raw `[u8; 32]` private key.
`write_to_file`	Encrypt a `Secret` and write a pretty-printed JSON keystore file. Returns the `Keystore`.

End-to-end example

use {
    anyhow::Result,
    dango_sdk::{Keystore, Secp256k1, Secret},
};
 
fn round_trip() -> Result<()> {
    let secret = Secp256k1::new_random();
    let pubkey = secret.public_key();
 
    Keystore::write_to_file(&secret, "./key.json", "hunter2")?;
 
    let bytes  = Keystore::from_file("./key.json", "hunter2")?;
    let recovered = Secp256k1::from_bytes(bytes)?;
    assert_eq!(pubkey, recovered.public_key());
    Ok(())
}

Notes

from_file returns the raw private key bytes, not a Secret. Callers wrap it in Secp256k1::from_bytes or Eip712::from_bytes depending on the account's signing scheme.
The file contains the (unencrypted) compressed public key alongside the ciphertext. Treat the file as sensitive even though the private key itself is encrypted.
write_to_file is only valid for secrets whose Private type dereferences to [u8] and whose Public type fits in ByteArray<33> (both Secp256k1 and Eip712 qualify).