# 生成 1024 位長度的私鑰
openssl genrsa -out private-key.pem 1024

# 生成公鑰
openssl rsa -in private-key.pem -pubout -out public-key.pem

package utils

import (
 "crypto"
 "crypto/rand"
 "crypto/rsa"
 "crypto/sha1"
 "crypto/x509"
 "encoding/hex"
 "encoding/pem"
 "errors"
 "io/ioutil"
)

var (
 Privkey string
)

func Sign(s string) (string, error) {
 key, err := ioutil.ReadFile(Privkey)
 if err != nil {
  return "", err
 }
 r, err := encryptSHA1WithRSA(key, []byte(s))
 if err != nil {
  return "", err
 }
 return hex.EncodeToString(r), nil
}

func encryptSHA1WithRSA(key, data []byte) ([]byte, error) {
 block, _ := pem.Decode(key)
 if block == nil {
  return nil, errors.New("no PEM data is found")
 }

 private, err := x509.ParsePKCS1PrivateKey(block.Bytes)
 if err != nil {
  return nil, err
 }
 hashed := SHA1(data)
 return rsa.SignPKCS1v15(rand.Reader, private, crypto.SHA1, hashed)
}

func SHA1(data []byte) []byte {
 h := sha1.New()
 h.Write(data)
 return h.Sum(nil)
}

package utils

import (
 "crypto"
 "crypto/rsa"
 "crypto/sha1"
 "crypto/x509"
 "encoding/hex"
 "encoding/pem"
 "io/ioutil"
)

var (
 Pubkey  string
)

func VerifySig(origin, sig string) error {
 b, err := ioutil.ReadFile(Pubkey)
 if err != nil {
  return err
 }
 block, _ := pem.Decode(b)
 pub, err := x509.ParsePKIXPublicKey(block.Bytes)
 if err != nil {
  return err
 }
 hashed := SHA1([]byte(origin))
 sigBytes, err := hex.DecodeString(sig)
 if err != nil {
  return err
 }
 return rsa.VerifyPKCS1v15(pub.(*rsa.PublicKey), crypto.SHA1, hashed, []byte(sigBytes))
}

func SHA1(data []byte) []byte {
 h := sha1.New()
 h.Write(data)
 return h.Sum(nil)
}