panic: gob: type elliptic.p256Curve has no exported fields

Vango Lu 0
Viewed 55

I am trying to build a blockchain project when I'm catching an issue about gob Serialize. I have a struct Wallet which uses elliptic.P256() Curve struct, and when I'm trying to serialize Wallet, a bug of no exported fields occured.

Really hope for some help.

There is my code.

const walletFile = "Wallets.dat"

type Wallets struct {
    WalletsMap map[string]*Wallet
}

type Wallet struct {
    PrivateKey ecdsa.PrivateKey
    PublicKey []byte
}

func (w *Wallets) SaveWallets() {
    var content bytes.Buffer

    gob.Register(elliptic.P256())

    encoder := gob.NewEncoder(&content)
    err := encoder.Encode(&w)
    if err != nil {
        log.Panic(err)
    }

    err = ioutil.WriteFile(walletFile, content.Bytes(), 0644)
    if err != nil {
        log.Panic(err)
    }

}


func NewWallets() (*Wallets, error) {
    if _, err := os.Stat(walletFile); os.IsNotExist(err) {
        wallets := &Wallets{}
        wallets.WalletsMap = make(map[string]*Wallet)
        return wallets, err
    }

    fileContent, err := ioutil.ReadFile(walletFile)
    if err != nil {
        log.Panic(err)
    }

    var wallets Wallets
    gob.Register(elliptic.P256())
    decoder := gob.NewDecoder(bytes.NewReader(fileContent))
    err = decoder.Decode(&wallets)
    if err != nil {
        log.Panic(err)
    }

    return &wallets, nil
}

The issue

2022/09/18 19:42:33 gob: type elliptic.p256Curve has no exported fields
panic: gob: type elliptic.p256Curve has no exported fields
gob elliptic-curve go
1 Answers

What you seem to be trying to do here is serialize a P256 curve from the crypto/elliptic package. The issue is that the P256() function returns an interface called elliptic.Curve.

What this error is telling you is that the underlying type of the elliptic.Curve, in this case elliptic.p256Curve, doesn't have any fields that are exported (named with the first letter capitalized). Go's reflect package, which encoding/gob uses, only works on exported fields.

You might want to try using crypto/elliptic's Marshal() or GenerateKey() functions.

Arsen63310
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