package nostr import ( "crypto/sha256" "encoding/hex" "fmt" "time" "github.com/btcsuite/btcd/btcec/v2" "github.com/btcsuite/btcd/btcec/v2/schnorr" "github.com/valyala/fastjson" ) type Event struct { ID string PubKey string CreatedAt time.Time Kind int Tags Tags Content string Sig string } const ( KindSetMetadata int = 0 KindTextNote int = 1 KindRecommendServer int = 2 KindContactList int = 3 KindEncryptedDirectMessage int = 4 KindDeletion int = 5 ) // GetID serializes and returns the event ID as a string func (evt *Event) GetID() string { h := sha256.Sum256(evt.Serialize()) return hex.EncodeToString(h[:]) } // Serialize outputs a byte array that can be hashed/signed to identify/authenticate func (evt *Event) Serialize() []byte { // the serialization process is just putting everything into a JSON array // so the order is kept var arena fastjson.Arena arr := arena.NewArray() // version: 0 arr.SetArrayItem(0, arena.NewNumberInt(0)) // pubkey arr.SetArrayItem(1, arena.NewString(evt.PubKey)) // created_at arr.SetArrayItem(2, arena.NewNumberInt(int(evt.CreatedAt.Unix()))) // kind arr.SetArrayItem(3, arena.NewNumberInt(evt.Kind)) // tags arr.SetArrayItem(4, tagsToFastjsonArray(&arena, evt.Tags)) // content arr.SetArrayItem(5, arena.NewString(evt.Content)) return arr.MarshalTo(nil) } // CheckSignature checks if the signature is valid for the id // (which is a hash of the serialized event content). // returns an error if the signature itself is invalid. func (evt Event) CheckSignature() (bool, error) { // read and check pubkey pk, err := hex.DecodeString(evt.PubKey) if err != nil { return false, fmt.Errorf("event pubkey '%s' is invalid hex: %w", evt.PubKey, err) } pubkey, err := schnorr.ParsePubKey(pk) if err != nil { return false, fmt.Errorf("event has invalid pubkey '%s': %w", evt.PubKey, err) } // read signature s, err := hex.DecodeString(evt.Sig) if err != nil { return false, fmt.Errorf("signature '%s' is invalid hex: %w", evt.Sig, err) } sig, err := schnorr.ParseSignature(s) if err != nil { return false, fmt.Errorf("failed to parse signature: %w", err) } // check signature hash := sha256.Sum256(evt.Serialize()) return sig.Verify(hash[:], pubkey), nil } // Sign signs an event with a given privateKey func (evt *Event) Sign(privateKey string) error { h := sha256.Sum256(evt.Serialize()) s, err := hex.DecodeString(privateKey) if err != nil { return fmt.Errorf("Sign called with invalid private key '%s': %w", privateKey, err) } sk, _ := btcec.PrivKeyFromBytes(s) sig, err := schnorr.Sign(sk, h[:]) if err != nil { return err } evt.ID = hex.EncodeToString(h[:]) evt.Sig = hex.EncodeToString(sig.Serialize()) return nil }