Different serialization of SecretScalar depending on default-features, leads to deserialization error

[OrestisAlpos]

Let the following code in a fresh repo:

let mut rng = rand_dev::DevRng::new();
    let key_share_plaintext1 = dfns_key_import_common::KeySharePlaintext {
        secret_share: generic_ec::SecretScalar::<dfns_key_import_common::Secp256k1>::random(
            &mut rng,
        ),
        version: dfns_key_import_common::utils::VersionGuard,
        public_shares: Vec::new(),
    };
    let key_share_plaintext1 = serde_json::to_string(&key_share_plaintext1).unwrap();
    println!("{:?}", &key_share_plaintext1);

We can import generic-ec in two ways. A: generic-ec = { git = "https://github.com/dfns-labs/generic-ec", branch = "m", features = ["serde", "curve-secp256k1", "wasm"] } B: generic-ec = { git = "https://github.com/dfns-labs/generic-ec", branch = "m", default-features = false, features = ["serde", "curve-secp256k1", "wasm"] }

The output is different in each case. A: "{\"version\":1,\"secret_share\":{\"curve\":\"secp256k1\",\"scalar\":\"a975cfe60a7649f55abcc2461f4082a81100d9509f0b9e6ee1b90933330bc003\"},\"public_shares\":[]}" B: "{\"version\":1,\"secret_share\":{\"curve\":\"secp256k1\",\"scalar\":[129,246,35,161,33,118,114,128,230,85,106,60,213,139,216,47,171,195,164,195,136,54,156,175,82,247,162,86,106,168,244,105]},\"public_shares\":[]}" The difference is in the serialization of secret-share.

The problem comes if we add the following code, which simply deserializes the serialized data:

    let _: dfns_key_import_common::KeySharePlaintext<dfns_key_import_common::Secp256k1> =
        serde_json::from_str(&key_share_plaintext1).unwrap();

then import option B gives:

thread 'test' panicked at 'called `Result::unwrap()` on an `Err` value: Error("invalid type: sequence, expected bytes", line: 1, column: 58)'

[survived]

It doesn't lead to deserialization panic, it leads to deserialization error. Panic is caused by .unwrap() you wrote that should never be used in prod code. I'll investigate the error

[OrestisAlpos]

Yes, the code is taken from a test actually. But you are right, it leads to an error.