Library for SRTP (Secure Realtime Transport Protocol) 

Other

libsrtp

SIP and ENUM dialer for Android with ZRTP/SRTP encryption, SIP over TLS, ICE/TURN for NAT, G.729 and many other features

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Conversations is an open source XMPP/Jabber client for Android

A free and open source Jabber/XMPP client for Android. Easy to use, reliable, battery friendly. With built-in support for images, group chats and e2e encryption.

Design principles
• Be as beautiful and easy to use as possible without sacrificing security or privacy
• Rely on existing, well established protocols
• Do not require a Google Account or specifically Google Cloud Messaging (GCM)
• Require as little permissions as possible

Features
• End-to-end encryption with either OMEMO or OpenPGP
• Encrypted audio and video calls (DLTS-SRTP)
• Sending and receiving images
• Intuitive UI that follows Android Design guidelines
• Pictures / Avatars for your Contacts
• Syncs with desktop client
• Conferences (with support for bookmarks)
• Address book integration
• Multiple Accounts / unified inbox
• Very low impact on battery life

XMPP Features
Conversations works with every XMPP server out there. However XMPP is an extensible protocol. These extensions are standardized as well in so called XEP’s. Conversations supports a couple of those to make the overall user experience better. There is a chance that your current XMPP server does not support these extensions. Therefore to get the most out of Conversations you should consider either switching to an
XMPP server that does or - even better - run your own XMPP server for you and your friends.
These XEPs are - as of now:

• XEP-0065: SOCKS5 Bytestreams (or mod_proxy65). Will be used to transfer files if both parties are behind a firewall (NAT).
• XEP-0163: Personal Eventing Protocol for avatars
• XEP-0191: Blocking command lets you blacklist spammers or block contacts without removing them from your roster.
• XEP-0198: Stream Management allows XMPP to survive small network outages and changes of the underlying TCP connection.
• XEP-0280: Message Carbons which automatically syncs the messages you send to your desktop client and thus allows you to switch seamlessly from your mobile client to your desktop client and back within one conversation.
• XEP-0237: Roster Versioning mainly to save bandwidth on poor mobile connections
• XEP-0313: Message Archive Management synchronize message history with the server. Catch up with messages that were sent while Conversations was offline.
• XEP-0352: Client State Indication lets the server know whether or not Conversations is in the background. Allows the server to save bandwidth by withholding unimportant packages.
• XEP-0363: HTTP File Upload allows you to share files in conferences and with offline contacts. Requires an additional component on your server.

An encrypted, user friendly XMPP instant messaging client optimized for mobile

libsrtp

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Conversations (Jabber / XMPP)