package crypto import (	"crypto/ed25519"	crand "crypto/rand"	"encoding/binary"	"encoding/json"	"fmt"	"cerca/util"	"github.com/synacor/argon2id"	rand "math/rand") type Keypair struct {	Public  string `json:"public"`	Private string `json:"private"`} func GenerateKeypair() (Keypair, error) {	ed := util.Describe("generate public keypair")	pub, priv, err := ed25519.GenerateKey(nil)	if err != nil {		return Keypair{}, ed.Eout(err, "generating key")	}	return Keypair{Public: fmt.Sprintf("%x", pub), Private: fmt.Sprintf("%x", priv)}, nil} func (kp *Keypair) Marshal() ([]byte, error) {	jason, err := json.MarshalIndent(kp, "", " ")	if err != nil {		return []byte{}, util.Eout(err, "marshal keypair")	}	return jason, nil} func (kp *Keypair) Unmarshal(input []byte) error {	err := json.Unmarshal(input, &kp)	if err != nil {		return util.Eout(err, "unmarshal keypair")	}	return nil} func HashPassword(s string) (string, error) {	ed := util.Describe("hash password")	hash, err := argon2id.DefaultHashPassword(s)	if err != nil {		return "", ed.Eout(err, "hashing with argon2id")	}	return hash, nil} func ValidatePasswordHash(password, passwordHash string) bool {	err := argon2id.Compare(passwordHash, password)	if err != nil {		return false	}	return true} func GenerateVerificationCode() int {	var src cryptoSource	rnd := rand.New(src)	return rnd.Intn(999999)} type cryptoSource struct{} func (s cryptoSource) Seed(seed int64) {} func (s cryptoSource) Int63() int64 {	return int64(s.Uint64() & ^uint64(1<<63))} func (s cryptoSource) Uint64() (v uint64) {	err := binary.Read(crand.Reader, binary.BigEndian, &v)	if err != nil {		util.Check(err, "generate random verification code")	}	return v}