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Wheeler & Needham’s Tiny Encryption Algorithm in js form

simple but powerful encryption algorithm which provides strong encryption in just a few lines of concise, clear code

当前为 2015-09-01 提交的版本，查看 最新版本。

此脚本不应直接安装。它是供其他脚本使用的外部库，要使用该库请加入元指令 // @require https://update.cn-greasyfork.org/scripts/12124/71602/Wheeler%20%20Needham%E2%80%99s%20Tiny%20Encryption%20Algorithm%20in%20js%20form.js 

  1. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  2. /*  Block TEA (xxtea) Tiny Encryption Algorithm         (c) Chris Veness 2002-2014 / MIT Licence  */
  3. /*   - www.movable-type.co.uk/scripts/tea-block.html                                              */
  4. /*                                                                                                */
  5. /*  Algorithm: David Wheeler & Roger Needham, Cambridge University Computer Lab                   */
  6. /*             http://www.cl.cam.ac.uk/ftp/papers/djw-rmn/djw-rmn-tea.html (1994)                 */
  7. /*             http://www.cl.cam.ac.uk/ftp/users/djw3/xtea.ps (1997)                              */
  8. /*             http://www.cl.cam.ac.uk/ftp/users/djw3/xxtea.ps (1998)                             */
  9. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  10.  
  11. /* jshint node:true *//* global define, escape, unescape, btoa, atob */
  12. 'use strict';
  13.  
  14.  
  15. /**
  16.  * Tiny Encryption Algorithm
  17.  *
  18.  * @namespace
  19.  */
  20. var Tea = {};
  21.  
  22.  
  23. /**
  24.  * Encrypts text using Corrected Block TEA (xxtea) algorithm.
  25.  *
  26.  * @param   {string} plaintext - String to be encrypted (multi-byte safe).
  27.  * @param   {string} password - Password to be used for encryption (1st 16 chars).
  28.  * @returns {string} Encrypted text (encoded as base64).
  29.  */
  30. Tea.encrypt = function(plaintext, password) {
  31.     plaintext = String(plaintext);
  32.     password = String(password);
  33.  
  34.     if (plaintext.length == 0) return('');  // nothing to encrypt
  35.  
  36.     //  v is n-word data vector; converted to array of longs from UTF-8 string
  37.     var v = Tea.strToLongs(plaintext.utf8Encode());
  38.     //  k is 4-word key; simply convert first 16 chars of password as key
  39.     var k = Tea.strToLongs(password.utf8Encode().slice(0,16));
  40.     var n = v.length;
  41.  
  42.     v = Tea.encode(v, k);
  43.  
  44.     // convert array of longs to string
  45.     var ciphertext = Tea.longsToStr(v);
  46.  
  47.     // convert binary string to base64 ascii for safe transport
  48.     return ciphertext.base64Encode();
  49. };
  50.  
  51.  
  52. /**
  53.  * Decrypts text using Corrected Block TEA (xxtea) algorithm.
  54.  *
  55.  * @param   {string} ciphertext - String to be decrypted.
  56.  * @param   {string} password - Password to be used for decryption (1st 16 chars).
  57.  * @returns {string} Decrypted text.
  58.  */
  59. Tea.decrypt = function(ciphertext, password) {
  60.     ciphertext = String(ciphertext);
  61.     password = String(password);
  62.  
  63.     if (ciphertext.length == 0) return('');
  64.  
  65.     //  v is n-word data vector; converted to array of longs from base64 string
  66.     var v = Tea.strToLongs(ciphertext.base64Decode());
  67.     //  k is 4-word key; simply convert first 16 chars of password as key
  68.     var k = Tea.strToLongs(password.utf8Encode().slice(0,16));
  69.     var n = v.length;
  70.  
  71.     v = Tea.decode(v, k);
  72.  
  73.     var plaintext = Tea.longsToStr(v);
  74.  
  75.     // strip trailing null chars resulting from filling 4-char blocks:
  76.     plaintext = plaintext.replace(/\0+$/,'');
  77.  
  78.     return plaintext.utf8Decode();
  79. };
  80.  
  81.  
  82. /**
  83.  * XXTEA: encodes array of unsigned 32-bit integers using 128-bit key.
  84.  *
  85.  * @param   {number[]} v - Data vector.
  86.  * @param   {number[]} k - Key.
  87.  * @returns {number[]} Encoded vector.
  88.  */
  89. Tea.encode = function(v, k) {
  90.     if (v.length < 2) v[1] = 0;  // algorithm doesn't work for n<2 so fudge by adding a null
  91.     var n = v.length;
  92.  
  93.     var z = v[n-1], y = v[0], delta = 0x9E3779B9;
  94.     var mx, e, q = Math.floor(6 + 52/n), sum = 0;
  95.  
  96.     while (q-- > 0) {  // 6 + 52/n operations gives between 6 & 32 mixes on each word
  97.         sum += delta;
  98.         e = sum>>>2 & 3;
  99.         for (var p = 0; p < n; p++) {
  100.             y = v[(p+1)%n];
  101.             mx = (z>>>5 ^ y<<2) + (y>>>3 ^ z<<4) ^ (sum^y) + (k[p&3 ^ e] ^ z);
  102.             z = v[p] += mx;
  103.         }
  104.     }
  105.  
  106.     return v;
  107. };
  108.  
  109.  
  110. /**
  111.  * XXTEA: decodes array of unsigned 32-bit integers using 128-bit key.
  112.  *
  113.  * @param   {number[]} v - Data vector.
  114.  * @param   {number[]} k - Key.
  115.  * @returns {number[]} Decoded vector.
  116.  */
  117. Tea.decode = function(v, k) {
  118.     var n = v.length;
  119.  
  120.     var z = v[n-1], y = v[0], delta = 0x9E3779B9;
  121.     var mx, e, q = Math.floor(6 + 52/n), sum = q*delta;
  122.  
  123.     while (sum != 0) {
  124.         e = sum>>>2 & 3;
  125.         for (var p = n-1; p >= 0; p--) {
  126.             z = v[p>0 ? p-1 : n-1];
  127.             mx = (z>>>5 ^ y<<2) + (y>>>3 ^ z<<4) ^ (sum^y) + (k[p&3 ^ e] ^ z);
  128.             y = v[p] -= mx;
  129.         }
  130.         sum -= delta;
  131.     }
  132.  
  133.     return v;
  134. };
  135.  
  136.  
  137. /**
  138.  * Converts string to array of longs (each containing 4 chars).
  139.  * @private
  140.  */
  141. Tea.strToLongs = function(s) {
  142.     // note chars must be within ISO-8859-1 (Unicode code-point <= U+00FF) to fit 4/long
  143.     var l = new Array(Math.ceil(s.length/4));
  144.     for (var i=0; i<l.length; i++) {
  145.         // note little-endian encoding - endianness is irrelevant as long as it matches longsToStr()
  146.         l[i] = s.charCodeAt(i*4)        + (s.charCodeAt(i*4+1)<<8) +
  147.               (s.charCodeAt(i*4+2)<<16) + (s.charCodeAt(i*4+3)<<24);
  148.     }
  149.     return l; // note running off the end of the string generates nulls since bitwise operators
  150. };            // treat NaN as 0
  151.  
  152.  
  153. /**
  154.  * Converts array of longs to string.
  155.  * @private
  156.  */
  157. Tea.longsToStr = function(l) {
  158.     var a = new Array(l.length);
  159.     for (var i=0; i<l.length; i++) {
  160.         a[i] = String.fromCharCode(l[i] & 0xFF, l[i]>>>8 & 0xFF, l[i]>>>16 & 0xFF, l[i]>>>24 & 0xFF);
  161.     }
  162.     return a.join('');  // use Array.join() for better performance than repeated string appends
  163. };
  164.  
  165.  
  166. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  167.  
  168.  
  169. /** Extend String object with method to encode multi-byte string to utf8
  170.  *  - monsur.hossa.in/2012/07/20/utf-8-in-javascript.html */
  171. if (typeof String.prototype.utf8Encode == 'undefined') {
  172.     String.prototype.utf8Encode = function() {
  173.         return unescape( encodeURIComponent( this ) );
  174.     };
  175. }
  176.  
  177. /** Extend String object with method to decode utf8 string to multi-byte */
  178. if (typeof String.prototype.utf8Decode == 'undefined') {
  179.     String.prototype.utf8Decode = function() {
  180.         try {
  181.             return decodeURIComponent( escape( this ) );
  182.         } catch (e) {
  183.             return this; // invalid UTF-8? return as-is
  184.         }
  185.     };
  186. }
  187.  
  188.  
  189. /** Extend String object with method to encode base64
  190.  *  - developer.mozilla.org/en-US/docs/Web/API/window.btoa, nodejs.org/api/buffer.html
  191.  *  note: if btoa()/atob() are not available (eg IE9-), try github.com/davidchambers/Base64.js */
  192. if (typeof String.prototype.base64Encode == 'undefined') {
  193.     String.prototype.base64Encode = function() {
  194.         if (typeof btoa != 'undefined') return btoa(this); // browser
  195.         if (typeof Buffer != 'undefined') return new Buffer(this, 'utf8').toString('base64'); // Node.js
  196.         throw new Error('No Base64 Encode');
  197.     };
  198. }
  199.  
  200. /** Extend String object with method to decode base64 */
  201. if (typeof String.prototype.base64Decode == 'undefined') {
  202.     String.prototype.base64Decode = function() {
  203.         if (typeof atob != 'undefined') return atob(this); // browser
  204.         if (typeof Buffer != 'undefined') return new Buffer(this, 'base64').toString('utf8'); // Node.js
  205.         throw new Error('No Base64 Decode');
  206.     };
  207. }
  208.  
  209.  
  210. /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -  */
  211. if (typeof module != 'undefined' && module.exports) module.exports = Tea; // CommonJS export
  212. if (typeof define == 'function' && define.amd) define([''], function() { return Tea; }); // AMD