Pidgin-Encryption is described as 'Encryption plugin for Pidgin, providing up to 4096 bit RSA encryption using the NSS crypto library from Mozilla. Keys are automatically transmitted and stored, making it very easy to use, but also resistant to man-in-the-middle attacks'. There are more than 25 alternatives to Pidgin-Encryption for a variety of platforms, including Android, iPhone, Windows, Linux and Mac. The best alternative is Signal, which is both free and Open Source. Other great apps like Pidgin-Encryption are Element (Free Personal, Open Source), Tox (Free, Open Source), Jami (Free, Open Source) and ChatSecure (Free, Open Source).
Signal is a messaging app with an unexpected focus on privacy, combined with all the features expected from a modern IM app. Signal has received a lot of praise from all around the world for its security and privacy-respecting technologies.
Element is a secure collaboration and messaging app based on the Matrix protocol. It’s decentralised to deliver digital sovereignty, and based on an open standard for easy connections and interoperability. It is end-to-end encrypted by default.
Jami (formerly GNU Ring, SFLphone) positions itself as a potential free Skype replacement Open Source and cross-platform. Jami gives you a full control over your communications and an unmatched level of privacy.
ChatSecure is a free and open source messaging app that features OTR encryption over XMPP. You can connect to your existing accounts on Facebook or Google, create new accounts on public XMPP servers(including via Tor), or even connect to your own server for extra security.
Bitmessage is a P2P communications protocol used to send encrypted messages to another person or to many subscribers. It is decentralized and trustless, meaning that you need-not inherently trust any entities like root certificate authorities.
FluffyChat is an open, nonprofit and cute matrix messenger app for Ubuntu Touch, Android and iOS. Open Opensource and open development where everyone can join. Nonprofit FluffyChat is donation funded. Cute ? Cute design and many theme settings including a dark mode.
Technitium Bit Chat is a secure, peer-to-peer (p2p), open source instant messenger designed to provide end-to-end encryption. It can be used over Internet and private LAN networks for instant messaging and file transfer.
Off-the-Record (OTR) Messaging allows you to have private conversations over any instant messaging (MSN,Gtalk, Facebook and so on) by providing encryption, authentication, deniability, perfect forward secrecy