Crypter

An innovative, convenient and secure crypto app.

Encrypt unlimited bits. Remember only a bit.

Crypter is an innovative, convenient and secure cross-platform crypto app that simplifies secure password generation and management by requiring you to only remember one bit, the MasterPass.

This is based on Crypto.Sync (an end-to-end cloud encryption client) which is a more elaborate implementation of the idea. So please check it out as well!

Link to this page: https://git.io/Crypter.info

Installation

All prebuilt binaries for all major platforms are available under releases.

Crypter is also available to install via Homebrew Cask for macOS, simply run the following command in the Terminal

$ brew cask install crypter

Status

Crypter v2.0 is a fully fledged crypto app that can decrypt and encrypt any arbitrary data. This version has been released and fully tested for macOS (OSX), Linux (for all distros via AppImage) and Windows (32 & 64 bit). All internal modules are fully tested (90%+ coverage). Some end-to-end tests have been written (see test/ui/test.js) but end-to-end testing is still mostly a WIP.

The next major release is v3.0 and any work for it is done on the "dev" branch. All features to be implemented for the next major version can be found at https://github.com/HR/Crypter/milestones/v3.0. Feel free to send PRs to speed this up!

If you have any suggestions then please open an issue!

Screens (some of them)

Crypto

One key to derive them all!

Crypter uses a MasterPass (obtained at setup) to derive a MasterPassKey using the PBKDF2 key derivation algorithm from the MasterPass (see below for spec). It then derives very secure encryption keys that are used for the encryption of files from the MasterPassKey using the PBKDF2 key derivation algorithm again. This method allows for the generation of very secure encryption keys for data encryption. Moreover, by just publicly storing the credentials used to derive the MasterPassKey and the salts used to derive the encryption keys you have the flexibility of deriving the encryption keys whenever you need to and not having to worry about storing them securely. All you have to do is remember your MasterPass.

Crypter never ever directly uses your MasterPass to encrypt anything but instead derives a MasterPassKey from it which it then uses to derive the encryption key (which is used directly to encrypt your file). Every time a file is decrypted, the encryption key is re-derived from the MasterPassKey. Every time you set the MasterPass through the setup or reset it (through Verify MasterPass), the MasterPassKey is derived from the MasterPass using a newly generated set of (random) credentials. These credentials are used to re-derive the MasterPassKey every time the Crypter is executed (i.e. the app is launched).

Authentication is used by default since the AES-256-GCM symmetric block cipher is used.

// Crypto defaults
let defaults = {
  iterations: 50000, // file encryption key derivation iterations
  keyLength: 32, // encryption key length
  ivLength: 12, // initialisation vector length
  algorithm: 'aes-256-gcm', // encryption algorithm
  digest: 'sha256', // PBKDF2 hash function
  hash_alg: 'sha256', // default hashing function
  mpk_iterations: 100000 // MasterPassKey derivation iterations
}

Encryption process

When encrypting a file, Crypter first creates a temporary hidden directory, namely '.crypting'. It then encrypts the user selected file with the crypto defaults and flushes the encrypted data to a file in the directory, namely 'data'. Furthermore, it writes the public credentials to a file within the same directory, namely 'creds'. Finally, Crypter compresses the directory to a tar archive with the name of the user selected file and the '.crypto' extension appended to it.

Decryption process

The decryption process is essentially the inverse of the encryption process where the temporary hidden directory is named '.decrypting'. The credentials are read from the creds file and used to decrypt the data file to the original user file with its original extension which is deduced from the crypto file name (e.g. extension for "file.txt.crypto" would be ".txt").

Crypto file format

A .crypto file is the product of the Crypter encryption process. It stores both the encrypted version of the user selected file and the public credentials used to encrypt it (and needed to decrypt it). The file itself it is a tar archive with the following structure:

someFile.crypto
├── data // the encrypted version of the user selected file
└── creds // the public credentials used to encrypt it

Public credentials

Certain credentials are required to decrypt the encrypted data as they are needed to reconstruct the particular encryption key and verify data integrity. These can be stored publicly without compromising security as it is fairly impossible (by current standards) to reconstruct the encryption key without the MasterPass and its credentials. The credentials are stored in the creds file of the .crypto archive (as delineated above) in the following format:

Crypter#iv#authTag#salt

Portability

When you encrypt a crypto file on one machine with Crypter and try to decrypt it with Crypter running on a different machine then you most probably will come across the following error:

ERROR: Unsupported state or unable to authenticate data

What happens is that the MasterPassKey originally used to derive the encryption key on one machine is not the same as the MasterPassKey derived on a different machine because the set of credentials generated on the other machine is different (due to randomness). As a result your encryption key that is derived from the MasterPassKey is different and so incorrect which yields the error.

Full portability

To achieve full portability the set of (MasterPassKey) credentials need to be exported from Crypter on one machine and imported into Crypter on another machine. The functionality is currently being implemented, see #6 for v3.0.

Security

Security-first practice

Crypter follows a security-first practice. This means that security is the highest priority and first consideration. This means that, while Crypter seeks to make encryption more convenient, Crypter chooses a convenient trade-off over a higher level of security.

MasterPassKey

Crypter uses a WeakMap to store the MasterPassKey inside the MasterPassKey class using closure function. This makes the MasterPassKey data held in the object (externally) inaccessible to an extent which increases the protection of the MasterPassKey. The MasterPassKey is never flushed to the filesystem and always kept in (main) memory. Since JS does not give control over or allow such a low-level operation as wiping memory, the program relies on the garbage collection and volatility of the main memory for the permanent erasure of the MasterPassKey stored in memory.

A decent number of iterations (see above specs) are used for the derivation of the MasterPassKey to mitigate brute-force attacks. A good amount of iterations are used for the derivation of the encryption keys from the MasterPasKey this is so that performance and speed is not significantly compromised. For critical application, you may choose to select 10,000,000 iterations instead (in app/src/crypto.js). Refer to http://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-132.pdf for more info

Crypter generates a new set of random credentials for deriving the MasterPassKey every time the MasterPass is set (at setup) or reset. Using randomness, mitigate brute-force attacks which drastically improves security.

Dev

The "dev" branch is the development branch and may be unstable. However the "master" branch will always be kept stable. So issue pull requests for improvements mainly on the dev branch.

Install (dependencies)

To install all dependencies run

$ npm install

Run

Uses gulp for a few things (so install gulp it globally if haven't already) and so to start the app simply run

$ gulp

Test

Uses mainly mocha (+ chai) for testing. Since the project uses a lot of JS ES6 syntax, babel is used as a transpiler. To run all the tests

$ npm test

Uses istanbul for coverage. To run test coverage

$ gulp coverage

Build

Binaries (available under releases) have been build using Electron v1.1.3. Crypter uses electron-builder to build binaries so install it globally first prior to any build

$ npm install electron-builder@next -g

The following instructions are for building Crypter on and for the respective platform stated

To build the app for your macOS

$ build -m

To build the app for your Linux

$ sudo apt-get install --no-install-recommends -y icnsutils graphicsmagick xz-utils
$ build -l --x64 --ia32

To build the app for your Windows x84 and/or x64

$ build -w --x64 --ia32

License

The MIT License (MIT)

Copyright (c) Habib Rehman (https://git.io/HR)

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished todo so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.