Warning: The Android operating system provided with phones and tablets is often modified with the addition of proprietary applications from Google or others and may compromise your privacy. We strongly recommend replacing it with Replicant (or compile Android from source for your device).
A must read: Mission Impossible: Hardening Android for Security and Privacy, by Mike Perry at The Tor Blog.
“Off-the-Record Messaging, commonly referred to as OTR, is a cryptographic protocol that provides strong encryption for instant messaging conversations. OTR uses a combination of the AES symmetric-key algorithm, the Diffie–Hellman key exchange, and the SHA-1 hash function. In addition to authentication and encryption, OTR provides perfect forward secrecy and malleable encryption.
The primary motivation behind the protocol was providing deniability for the conversation participants while keeping conversations confidential, like a private conversation in real life, or off the record in journalism sourcing.”
iOS and WP are proprietary operating systems whose source code are not available for auditing by third parties. You should entrust neither your communications nor your data to a black box device.
Installing your own add-ons into Tor Browser is not recommended, as they may bypass Tor or otherwise harm your anonymity and privacy. Check the EFF's Panopticlick to see how trackable your browser configuration is by third parties.
If you're using a Firefox-based browser, you can safeguard your browsing habits and stop advertising companies from tracking you by installing uBlock Origin, Request Policy, and HTTPS Everywhere.
A more advanced alternative to Request Policy would be uMatrix.
Why is Adblock Plus not recommended? Adblock Plus shows “acceptable ads” by default, which works against the purpose of the add-on. Either disable acceptable ads or use uBlock Origin instead.
There is also a DuckDuckGo hidden service at 3g2upl4pq6kufc4m.onion for Tor users.
MetaGer is a SaaS by the German non-profit SUMA e.V. that provides you with anonymous meta search results.
Startpage is a SaaS hosted in the USA and the Netherlands that provides you with anonymous Google search and image results through a free proxy.