Building a Signing Server

 Posted on December 18, 2017  |  Hans-Christoph Steiner

The Android APK signing model sets the expectation that the signing key will be the same for the entire lifetime of the app. That can be seen in the recommended lifetype of an Android signing key: 20+ years. On top of that, it is difficult to migrate an app to a new key. Since the signing key is an essential part to preventing APKs from impersonating another, Android signing keys must be kept safe for the entire life of the app. [Read More]
bazaar  F-Droid  fdroid  hardware  howto  hsm  identity  security  signing  signing key  smart card  tor 

Building the most private app store

 Posted on June 2, 2016  |  Hans-Christoph Steiner

App stores can work well without any tracking at all Attackers are increasingly seeing app stores as a prime attack vector, whether it is aimed at the masses like XCodeGhost or very targeted like in FBI vs Apple. When we install software from an app store, we are placing a lot of trust in a lot of different parties involved in getting the source code from the original developer delivered to our device in a useful form. [Read More]
Android  anonymity  bazaar  debian  encryption  F-Droid  fdroid  identity  mobile  open source  privacy  reproducible builds  security  tor 

How to Migrate Your Android App’s Signing Key

 Posted on December 29, 2015  |  Abel Luck

It is time to update to a stronger signing key for your Android app! The old default RSA 1024-bit key is weak and officially deprecated. What? The Android OS requires that every application installed be signed by a digital key. The purpose behind this signature is to identify the author of the application, allow this author and this author alone to make updates to the app, as well as provide a mechanism to establish inter-application trust. [Read More]
Android  bazaar  encryption  F-Droid  fdroid  howto  identity  rsa  security  signing key  TrustedIntents 

Introducing TrustedIntents for Android

 Posted on July 30, 2014  |  Hans-Christoph Steiner

Following up on our research on secure Intent interactions, we are now announcing the first working version of the TrustedIntents library for Android. It provides methods for checking any Intent for whether the sending and receiving app matches a specified set of trusted app providers. It does this by “pinning” to the signing certificate of the APKs. The developer includes this “pin” in the app, which includes the signing certificate to trust, then TrustedIntents checks Intents against the configured certificate pins. [Read More]
Android  identity  martusvmm  security  usability 

Security in a thumb drive: the promise and pain of hardware security modules, take one!

 Posted on March 28, 2014  |  Hans-Christoph Steiner

Hardware Security Modules (aka Smartcards, chipcards, etc) provide a secure way to store and use cryptographic keys, while actually making the whole process a bit easier. In theory, one USB thumb drive like thing could manage all of the crypto keys you use in a way that makes them much harder to steal. That is the promise. The reality is that the world of Hardware Security Modules (HSMs) is a massive, scary minefield of endless technical gotchas, byzantine standards (PKCS#11! [Read More]
Android  ant  bazaar  encryption  hardware  howto  hsm  identity  jarsigner  keytool  openssl  smartcard 

Integrating Crypto Identities with Android

 Posted on December 28, 2013  |  Hans-Christoph Steiner

ver the past couple of years, Android has included a central database for managing information about people, it is known as the ContactsContract (that’s a mouthful). Android then provides the People app and reusable interface chunks to choose contacts that work with all the information in the ContactsContract database. Any time that you are adding an account in the Settings app, you are setting up this integration. You can see it with Google services, Skype, Facebook, and many more. [Read More]
Android  encryption  gnupg  gpg  identity  openpgp  otr  pgp  psst  usability 

Keys, signatures, certificates, verifications, etc. What are all these for?

 Posted on December 12, 2013  |  Hans-Christoph Steiner

For the past two years, we have been thinking about how to make it easier for anyone to achieve private communications. One particular focus has been on the “security tokens” that are required to make private communications systems work. This research area is called internally Portable Shared Security Tokens aka PSST. All of the privacy tools that we are working on require “keys” and “signatures”, to use the language of cryptography, and these are the core of what “security tokens” are. [Read More]
encryption  identity  nfc  openpgp  otr  pgp  privacy  psst  qrcode  secure introductions  security  trust  usability 

Getting keys into your keyring with Gnu Privacy Guard for Android

 Posted on December 6, 2013  |  Hans-Christoph Steiner

Now that you can have a full GnuPG on your Android device with Gnu Privacy Guard for Android, the next step is getting keys you need onto your device and included in Gnu Privacy Guard. We have tried to make it as easy as possible without compromising privacy, and have implemented a few approaches, while working on others. There are a few ways to get this done right now. Gnu Privacy Guard registered itself with Android as a handler of all the standard OpenPGP MIME types (application/pgp-keys, application/pgp-encrypted, application/pgp-signature), as well as all of the OpenPGP and GnuPG file extensions (. [Read More]
Android  encryption  gnupg  gpg  howto  identity  open source  openpgp  pgp  privacy  psst  security 

On Verifying Identity Using Cryptography

 Posted on March 19, 2012  |  Hans-Christoph Steiner

One of the most important uses of cryptography these days is verifying the identity of the other side of a digital conversation. That conversation could be between two people using OTR-encrypted IM, a web browser showing a bank website, a Debian Developer uploading a package to the Debian build server, an ssh client logging into an ssh server, and on and on. In all of these cases, cryptography is used to ensure that the software is indeed receiving replies from the expected entity. [Read More]
crypto  https  identity  openpgp  otr  psst  signing  ssh