鸿蒙harmony加解密算法 写法封装

最近在看harmony。网络通讯最基础的数据加解密需要封装，以下研究了其写法。其实写法和flutter里 甚至android中代码写法 大同小异，具体算法可自定义修改，只展示原理。

原理：

加密：1.json字符串（待加密原文）通过base64执行decodeSync 2.通过算法转换为byte数组 3.byte转string

解密：1.string  json字符串（密文） 转byte       2.通过算法得到新byte数组         3.通过base64的encodeToStringSync 把byte转为string

import util from '@ohos.util';

/**
 * 加解密 位移符占位数
 */
static readonly PACKET_HEADER_SIZE: number = 5;

/**
 * 加密算法
 * @param strBuf
 * @returns
 */
public decryption(strBuf: string): string {
  var base64 = new util.Base64Helper();
  let pBuffer = base64.decodeSync(strBuf);
  var strBuffer = "";
  var pNewBuffer = new Array(pBuffer.length - CommonConstants.PACKET_HEADER_SIZE);
  let iSize = pBuffer.length;

  if (pBuffer[0] != 0) {
    for (let i = CommonConstants.PACKET_HEADER_SIZE; i < iSize; i++) {
      let t1 = ((pBuffer[i] & 0xFF) ^ ((pBuffer[0] & 0xFF) ^ (iSize - i))) % 256;
      if (t1 < 0) {
        t1 = t1 + 256;
      }
      pNewBuffer[i - CommonConstants.PACKET_HEADER_SIZE] = t1;
      let t2 = ((pNewBuffer[i - CommonConstants.PACKET_HEADER_SIZE] & 0xFF) - ((i - CommonConstants.PACKET_HEADER_SIZE) ^ (pBuffer[0] & 0xFF))) % 256;
      // 取余数时 负数 加 256
      if (t2 < 0) {
        t2 = t2 + 256;
      }
      // pNewBuffer[i - PACKET_HEADER_SIZE] = Convert.ToByte(t2);
      pNewBuffer[i - CommonConstants.PACKET_HEADER_SIZE] = t2;
    }

    strBuffer = this.byteToString(pNewBuffer);
  }
  return strBuffer;
}


/**
 *  解密算法
 * @param strBuf
 * @param bEncryption
 * @returns
 */
public encryption(strBuf: string,bEncryption: boolean): string {
  var base64 = new util.Base64Helper();
  var pSndBuf = new Array();

  pSndBuf = this.stringToByte(strBuf);

  var iSize = pSndBuf.length;
  let pTempBuffer = new Uint8Array(pSndBuf.length + CommonConstants.PACKET_HEADER_SIZE);
  if (bEncryption) {
    var rd = Math.random() * 1000;
    pTempBuffer[0] = rd % 128;
  } else {
    pTempBuffer[0] = 0;
  }
  var iLength = (iSize + CommonConstants.PACKET_HEADER_SIZE);

  var byteLength = new Array(iLength);

  pTempBuffer[1] = byteLength[0];
  pTempBuffer[2] = byteLength[1];
  if (pTempBuffer[0] != 0) {
    for (let i = 0; i < iSize; i++) {
      pTempBuffer[CommonConstants.PACKET_HEADER_SIZE + i] = (((pSndBuf[i] & 0xFF) + (i ^ ((pTempBuffer[0] & 0xFF)))) % 256);
      pTempBuffer[CommonConstants.PACKET_HEADER_SIZE + i] = (((pTempBuffer[CommonConstants.PACKET_HEADER_SIZE + i] & 0xFF) ^ ((pTempBuffer[0] & 0xFF) ^ (iSize - i))) % 256);
    }
  } else {
    for (let i = 0; i < iSize; i++) {
      pTempBuffer[CommonConstants.PACKET_HEADER_SIZE + i] = pSndBuf[i];
    }
  }
  return base64.encodeToStringSync(pTempBuffer);
}


/**
 * string转byte
 * @param str
 * @returns
 */
public stringToByte(str) {
  var bytes = new Array();
  var len,c;
  len = str.length;
  for (var i = 0; i < len; i++) {
    c = str.charCodeAt(i);
    if (c >= 0x010000 && c <= 0x10FFFF) {
      bytes.push(((c >> 18) & 0x07) | 0xf0);
      bytes.push(((c >> 12) & 0x3F) | 0x80);
      bytes.push(((c >> 6) & 0x3f) | 0x80);
      bytes.push((c & 0x3F) | 0x80);
    } else if (c >= 0x000800 && c <= 0x00FFF) {
      bytes.push(((c >> 12) & 0x07) | 0xf0);
      bytes.push(((c >> 6) & 0x3F) | 0x80);
      bytes.push((c & 0x3F) | 0x80);
    } else if (c >= 0x000800 && c <= 0x0007FF) {
      bytes.push(((c >> 6) & 0x3F) | 0x80);
      bytes.push((c & 0x3F) | 0x80);
    } else {
      bytes.push(c & 0xFF)
    }
  }
  return bytes;
}

/**
 * byte转string
 * @param str
 * @returns
 */
public byteToString(arr): string {
  if (typeof arr === 'string') {
    return arr;
  }
  var str = '',_arr = arr;
  for (var i = 0; i < _arr.length; i++) {
    var one = _arr[i].toString(2),v = one.match(/^1+?(?=0)/);
    if (v && one.length == 8) {
      var bytesLength = v[0].length;
      var store = _arr[i].toString(2).slice(7 - bytesLength);
      for (var st = 1; st < bytesLength; st++) {
        store += _arr[st + i].toString(2).slice(2);
      }
      str += String.fromCharCode(parseInt(store,2));
      i += bytesLength - 1;
    } else {
      str += String.fromCharCode(_arr[i]);
    }
  }
  return str;
}

用法：
CommonUtils.encryption(needEncryption.toString(),true);
CommonUtils.decryption(resultJson.Body.toString());