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. It is a core component of OpenWrt and other router distributions.
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. Supports elliptic curve cryptography for key exchange and public key authentication as of version 2013.62.