Dropbear is a software package written by Matt Johnston that provides a Secure Shell-compatible server and client. It is designed as a replacement for standard OpenSSH for environments with low memory and processor resources, such as embedded systems.
Dropbear implements version 2 of the Secure Shell (SSH) protocol.
The cryptographic algorithms are implemented using third-party cryptographic libraries included internally in the Dropbear distribution. It derives some parts from OpenSSH to handle BSD-style pseudo terminals.
Dropbear implements the complete SSH version 2 protocol in both the client and the server. It does not support SSH version 1 backwards-compatibility to save space and resources, and to avoid the inherent security vulnerabilities in SSH version 1. SCP is also implemented. SFTP support relies on a binary file which can be provided by OpenSSH or similar programs. FISH works in any case and is supported e.g. by Konqueror.