Retroshare is a decentralized open source friend-to-friend (F2F) Instant Messenger tool with group file haring capabilities and encryption, friends need to be invited before they are able to take part in the chat, you can create a group chat using a friends list, in group chats a forum can be used to distribute files in between acquaintances, the files are distributed in a multihop swarm system, even if one person goes offline, the files are still available as they can be downloaded from more than one source in parallel.
It is possible to post links on a public chatroom, the links are on the form of “retroshare://” and whoever clicks on them will need to have the software installed for them to work, this is an ideal program to securely transfer files in between friends with no central server keeping logs and your private encryption key kept in your hard disk with no possibility of leaking it out. Authentication is done using GnuPG encryption keys (GPG4Win is included in the Windows installer), connection is through SSH and OpenSSL is used for end to end encryption.
Upload and download speeds will depend on the user’s available bandwidth, file sizes of more than 2GB are supported, a private friend to friend network like Retroshare solves the problem of strangers reporting on controversial files being shared but friends IPs are still visible and if someone steals a members identity the whole network will fall, due to its multiphop nature the original uploader might hide his computer’s IP from the person downloading from him but other people IPs sharing that file in the network will be visble, leading to the original source following them, disabling IP/certificate exchange services improves anonymity.
You can use Retroshare with a Virtual Private Network (VPN) to hide your real IP and improve your network anonymity, as VPNs are known to keep logs for a shorter time than ISPs do, there are no VPN incompatibilities of any kind, the software is available for Windows, Linux and MAC.