implemented first of the fallback crypto functions

.gitignore

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+node_modules/

browserify/crypto-index.js

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+;(function () {
+'use strict';
+
+  var createHash = require('create-hash');
+  var pbkdf2 = require('pbkdf2');
+  var aes = require('browserify-aes');
+
+  exports.sha256 = function (buf) {
+    var hash = createHash('sha256');
+    hash.update(buf);
+    hash.end();
+    return Promise.resolve(hash.read());
+  };
+
+  exports.encrypt = function (data, password, salt, iv) {
+    // Derived AES key is 128 bit, and the function takes a size in bytes.
+    var aesKey = pbkdf2.pbkdf2Sync(password, Buffer(salt), 8192, 16, 'sha256');
+    var cipher = aes.createCipheriv('aes-128-gcm', aesKey, Buffer(iv));
+    var result = Buffer.concat([cipher.update(Buffer(data)), cipher.final(), cipher.getAuthTag()]);
+    return Promise.resolve(result);
+  };
+
+  exports.decrypt = function (data, password, salt, iv) {
+    var aesKey = pbkdf2.pbkdf2Sync(password, Buffer(salt), 8192, 16, 'sha256');
+    var decipher = aes.createDecipheriv('aes-128-gcm', aesKey, Buffer(iv));
+
+    decipher.setAuthTag(Buffer(data.slice(-16)));
+    var result = Buffer.concat([decipher.update(Buffer(data.slice(0, -16))), decipher.final()]);
+    return Promise.resolve(result);
+  };
+
+}());

gulpfile.js

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+;(function () {
+  'use strict';
+
+  var gulp = require('gulp');
+  var browserify = require('browserify');
+  var source = require('vinyl-source-stream');
+  var streamify = require('gulp-streamify');
+  var uglify = require('gulp-uglify');
+  var rename = require('gulp-rename');
+
+  gulp.task('default', function () {
+    return browserify('./browserify/crypto-index.js', {standalone: 'OAUTH3_crypto'}).bundle()
+      .pipe(source('browserify/crypto-index.js'))
+      .pipe(rename('oauth3.crypto.js'))
+      .pipe(gulp.dest('./'))
+      .pipe(streamify(uglify()))
+      .pipe(rename('oauth3.crypto.min.js'))
+      .pipe(gulp.dest('./'))
+      ;
+  });
+}());

package.json

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+{
+  "name": "oauth3",
+  "respository": {
+    "type": "git",
+    "url": "git+ssh://git@git.daplie.com:Daplie/oauth3.js.git"
+  },
+  "scripts": {
+    "install": "./node_modules/.bin/gulp"
+  },
+  "devDependencies": {
+    "atob": "^2.0.3",
+    "browserify": "^14.1.0",
+    "browserify-aes": "^1.0.6",
+    "btoa": "^1.1.2",
+    "gulp": "^3.9.1",
+    "gulp-cli": "^1.2.2",
+    "gulp-rename": "^1.2.2",
+    "gulp-streamify": "^1.0.2",
+    "gulp-uglify": "^2.1.0",
+    "pbkdf2": "^3.0.9",
+    "vinyl-source-stream": "^1.1.0"
+  }
+}