Encryption and Decryption in Go

func PKCS7Padding(ciphertext []byte, blockSize int) []byte {
    padding := blockSize - len(ciphertext)%blockSize
    //The Repeat() function copies the slice []byte{byte(padding)} padding times, then merges it into a new byte slice and returns it
    padtext := bytes.Repeat([]byte{byte(padding)}, padding)
    return append(ciphertext, padtext...)
}

  //The reverse operation of padding: remove the padding string
  func PKCS7UnPadding(origData []byte) ([]byte, error) {
      //Get the data length
      length := len(origData)
      if length == 0 {
          return nil, errors.New("加密字符串错误！")
      } else {
          //Get the length of the padding string
          unpadding := int(origData[length-1])
          //Slice off, remove the padding bytes, and return the plaintext
          return origData[:(length - unpadding)], nil
      }
  }

  //Implement encryption
  func AesEcrypt(origData []byte, key []byte) ([]byte, error) {
      //Create an instance of the encryption algorithm
      block, err := aes.NewCipher(key)
      if err != nil {
          return nil, err
      }
      //Get the block size
      blockSize := block.BlockSize()
      //Pad the data so its length meets the requirement
      origData = PKCS7Padding(origData, blockSize)
      //Use CBC mode from the AES encryption methods
      blocMode := cipher.NewCBCEncrypter(block, key[:blockSize])
      crypted := make([]byte, len(origData))
      //Perform the encryption
      blocMode.CryptBlocks(crypted, origData)
      return crypted, nil
  }

  //Implement decryption
  func AesDeCrypt(cypted []byte, key []byte) ([]byte, error) {
      //Create an instance of the encryption algorithm
      block, err := aes.NewCipher(key)
      if err != nil {
          return nil, err
      }
      //Get the block size
      blockSize := block.BlockSize()
      //Create an instance of the decryption client
      blockMode := cipher.NewCBCDecrypter(block, key[:blockSize])
      origData := make([]byte, len(cypted))
      //This function can also be used for decryption
      blockMode.CryptBlocks(origData, cypted)
      //Remove the padding string
      origData, err = PKCS7UnPadding(origData)
      if err != nil {
          return nil, err
      }
      return origData, err
  }

  //Encrypt base64
  func EnPwdCode(pwd []byte) (string, error) {
      result, err := AesEcrypt(pwd, getKey())
      if err != nil {
          return "", err
      }
      return base64.StdEncoding.EncodeToString(result), err
  }

  //Decrypt
  func DePwdCode(pwd string) ([]byte, error) {
      //Decrypt the base64 string
      pwdByte, err := base64.StdEncoding.DecodeString(pwd)
      if err != nil || len(pwdByte) <= 0 {
          return nil, err
      }
      //Perform AES decryption
      return AesDeCrypt(pwdByte, getKey())
  }

  //Encrypt base64
  func EnPwdUserCode(pwd []byte) (string, error) {
      result, err := AesEcrypt(pwd, getUserKey())
      if err != nil {
          return "", err
      }
      return base64.StdEncoding.EncodeToString(result), err
  }

  //Decrypt
  func DePwdUserCode(pwd string) ([]byte, error) {
      //Decrypt the base64 string
      pwdByte, err := base64.StdEncoding.DecodeString(pwd)
      if err != nil || len(pwdByte) <= 0 {
          return nil, err
      }
      //Perform AES decryption
      return AesDeCrypt(pwdByte, getUserKey())
  }