OpenPGP Keychain (for Android)

OpenPGP Keychain is an OpenPGP implementation for Android. The development began as a fork of Android Privacy Guard (APG).

see http://sufficientlysecure.org/keychain

How to help the project?

Translate the application

Translations are managed at Transifex, please contribute there at https://www.transifex.com/projects/p/openpgp-keychain/

Contribute Code

1. Join the development mailinglist at http://groups.google.com/d/forum/openpgp-keychain-dev
2. Lookout for interesting issues on our issue page at Github: https://github.com/openpgp-keychain/openpgp-keychain/issues
3. Tell us about your plans on the mailinglist
4. Read this README, especially the notes about coding style
5. Fork OpenPGP Keychain and contribute code (the best part ;) )
6. Open a pull request on Github. I will help with occuring problems and merge your changes back into the main project.

I am happy about every code contribution and appreciate your effort to help us developing OpenPGP Keychain!

Development

Development mailinglist at http://groups.google.com/d/forum/openpgp-keychain-dev

Build with Gradle

1. Have Android SDK "tools", "platform-tools", and "build-tools" directories in your PATH (http://developer.android.com/sdk/index.html)
2. Open the Android SDK Manager (shell command: android).
   Expand the Tools directory and select "Android SDK Build-tools" newest version.
   Expand the Extras directory and install "Android Support Repository"
   Select everything for the newest SDK
3. Export ANDROID_HOME pointing to your Android SDK
4. Execute ./gradlew build
5. You can install the app with adb install -r OpenPGP-Keychain/build/apk/OpenPGP-Keychain-debug-unaligned.apk

Build API Demo with Gradle

1. Follow 1-3 from above
2. Change to API Demo directory cd OpenPGP-Keychain-API-Demo
3. Execute ./gradlew build

Development with Android Studio

I am using the newest Android Studio for development. Development with Eclipse is currently not possible because I am using the new project structure.

1. Clone the project from github
2. From Android Studio: File -> Import Project -> Select the cloned top folder
3. Import project from external model -> choose Gradle

Keychain API

Intent API

All Intents require user interaction, e.g. to finally encrypt the user needs to press the "Encrypt" button. To do automatic encryption/decryption/sign/verify use the OpenPGP Remote API.

Android Intent actions:

• android.intent.action.VIEW connected to .gpg and .asc files: Import Key and Decrypt
• android.intent.action.SEND connected to all mime types (text/plain and every binary data like files and images): Encrypt and Decrypt

OpenPGP Keychain Intent actions:

• org.sufficientlysecure.keychain.action.ENCRYPT
  • To encrypt or sign text, use extra text (type: String)
  • or set data Uri (intent.setData()) pointing to a file
  • Enable ASCII Armor for file encryption (encoding to Radix-64, 33% overhead) by adding the extra ascii_armor with value true
• org.sufficientlysecure.keychain.action.DECRYPT
  • To decrypt or verify text, use extra text (type: String)
  • or set data Uri (intent.setData()) pointing to a file
• org.sufficientlysecure.keychain.action.IMPORT_KEY
  • Extras: key_bytes (type: byte[])
  • or set data Uri (intent.setData()) pointing to a file
• org.sufficientlysecure.keychain.action.IMPORT_KEY_FROM_KEY_SERVER
  • Extras: query (type: String)
  • or fingerprint (type: String)
• org.sufficientlysecure.keychain.action.IMPORT_KEY_FROM_QR_CODE
  • without extras, starts Barcode Scanner to get QR Code

OpenPGP Keychain special registered Intents:

• android.intent.action.VIEW with URIs following the openpgp4fpr schema. For example: openpgp4fpr:718C070100012282. This is used in QR Codes, but could also be embedded into your website. (compatible with Monkeysphere's and Guardian Project's QR Codes)
• NFC (android.nfc.action.NDEF_DISCOVERED) on mime type application/pgp-keys (as specified in http://tools.ietf.org/html/rfc3156, section 7)

OpenPGP Remote API

To do asyncronous fast encryption/decryption/sign/verify operations bind to the OpenPGP remote service. The API Demo contains all required AIDL files and a demo activity.

Try out the API

Keychain: https://play.google.com/store/apps/details?id=org.sufficientlysecure.keychain
API Demo: https://play.google.com/store/apps/details?id=org.sufficientlysecure.keychain.demo

Design

All apps wanting to use this generic API just need to include the AIDL files and connect to the service. Other OpenPGP apps can implement a service based on this AIDL definition.

The API is designed to be as easy as possible to use by apps like K-9 Mail. The service definition defines sign/encrypt/signAndEncrypt/decryptAndVerify [1].

As can be seen the apps themselves never need handle key ids directly. Only user ids (emails) are used to define recipients. If more than one pub key exists for an email, OpenPGP Keychain will handle the problem by showing a selection screen.

Also app devs never need to fiddle with private keys. On first operation, OpenPGP Keychain shows an activity to allow or disallow access, while also allowing to choose the private key used for this app. Please try the Demo app out to see how it works [4].

Integration

The API is defined as AIDL interfaces in org.openintents.openpgp packge [2]. All files from [2] needs to be included in the project.

Using the OpenPgpServiceConnection.java [3] you can choose to which OpenPGP provider you want to connect (other pgp apps can implement the interfaces). They can be queried as shown in the demo app (see [3] how to query). If other OpenPGP apps implement the service, no additional code is required in k9mail per provider. See [3] for a complete example for integration.

[1] https://github.com/openpgp-keychain/openpgp-keychain/blob/master/OpenPGP-Keychain-API-Demo/src/org/openintents/openpgp/IOpenPgpService.aidl
[2] https://github.com/openpgp-keychain/openpgp-keychain/tree/master/OpenPGP-Keychain-API-Demo/src/org/openintents/openpgp
[3] https://github.com/openpgp-keychain/openpgp-keychain/blob/master/OpenPGP-Keychain-API-Demo/src/org/openintents/openpgp/OpenPgpServiceConnection.java
[3] https://github.com/openpgp-keychain/openpgp-keychain/blob/master/OpenPGP-Keychain-API-Demo/src/org/sufficientlysecure/keychain/demo/OpenPgpProviderActivity.java
[4] https://play.google.com/store/apps/details?id=org.sufficientlysecure.keychain.demo

Extended Remote API

TODO

Libraries

ZXing Barcode Scanner Android Integration

Classes can be found under "libraries/zxing-android-integration/".

1. Checkout their SVN (see http://code.google.com/p/zxing/source/checkout)
2. Copy all classes from their android-integration folder to our library folder

ZXing

Classes can be found under "libraries/zxing/". ZXing classes were extracted from the ZXing library (http://code.google.com/p/zxing/). Only classes related to QR Code generation are utilized.

Bouncy Castle

Spongy Castle

Spongy Castle is the stock Bouncy Castle libraries with a couple of small changes to make it work on Android. OpenPGP Keychain uses a forked version with some small changes. These changes will been sent to Bouncy Castle, and Spongy Castle will be used again when they have filtered down.

see

• Fork: https://github.com/openpgp-keychain/spongycastle
• Spongy Castle: http://rtyley.github.com/spongycastle/

Bouncy Castle resources

• Repository: https://github.com/bcgit/bc-java
• Issue tracker: http://www.bouncycastle.org/jira/browse/BJA

Documentation

• Documentation project at http://www.cryptoworkshop.com/guide/
• Tests in https://github.com/bcgit/bc-java/tree/master/pg/src/test/java/org/bouncycastle/openpgp/test
• Mailinglist Archive at http://bouncy-castle.1462172.n4.nabble.com/Bouncy-Castle-Dev-f1462173.html

Notes

Gradle Build System

We try to make our builds as reproducible/deterministic as possible. This is also a key requirement to be part of F-Droid. When changing build files or dependencies, respect the following requirements:

• No precompiled libraries. All libraries should be provided as sourcecode in "libraries" folder
• No dependencies from Maven
• Always use a fixed Android Gradle plugin version not a dynamic one, e.g. 0.7.3 instead of 0.7.+
• Commit the corresponding gradle wrapper version to the repository

Translations

Translations are hosted on Transifex, which is configured by ".tx/config".

1. To pull newest translations install transifex client (e.g. apt-get install transifex-client)
2. Config Transifex client with "~/.transifexrc"
3. Go into root folder of git repo
4. execute tx pull (tx pull -a to get all languages)

see http://help.transifex.net/features/client/index.html#user-client

Coding Style

Code

• Indentation: 4 spaces, no tabs
• Maximum line width for code and comments: 100
• Opening braces don't go on their own line
• Field names: Non-public, non-static fields start with m.
• Acronyms are words: Treat acronyms as words in names, yielding !XmlHttpRequest, getUrl(), etc.

See http://source.android.com/source/code-style.html

XML Eclipse Settings

• XML Maximum line width 999
• XML: Split multiple attributes each on a new line (Eclipse: Properties -> XML -> XML Files -> Editor)
• XML: Indent using spaces with Indention size 4 (Eclipse: Properties -> XML -> XML Files -> Editor)

See http://www.androidpolice.com/2009/11/04/auto-formatting-android-xml-files-with-eclipse/

Licenses

OpenPGP Kechain is licensed under GPLv3+. Some parts (older parts and some libraries are Apache License v2, MIT X11 License)

This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see http://www.gnu.org/licenses/.

Libraries

• SpongyCastle
  https://github.com/rtyley/spongycastle
  MIT X11 License

• Android Support Library v4
  http://developer.android.com/tools/support-library/index.html
  Apache License v2

• Android Support Library v7 'appcompat'
  http://developer.android.com/tools/support-library/index.html
  Apache License v2

• HtmlTextView
  https://github.com/dschuermann/html-textview
  Apache License v2

• ZXing
  http://code.google.com/p/zxing/
  Apache License v2

• StickyListHeaders
  https://github.com/emilsjolander/StickyListHeaders
  Apache License v2

• Android-Bootstrap
  https://github.com/Bearded-Hen/Android-Bootstrap
  MIT License

Images

• icon.svg
  modified version of kgpg_key2_kopete.svgz

• key.svg
  http://rrze-icon-set.berlios.de/
  Creative Commons Attribution Share-Alike licence 3.0

• Menu icons
  http://developer.android.com/design/downloads/index.html#action-bar-icon-pack