The ssh library was designed to be used by programmers needing a working SSH
implementation by the mean of a library. The complete control of the client is
made by the programmer. With libssh, you can remotely execute programs, transfer
files, use a secure and transparent tunnel for your remote programs.
With its Secure FTP implementation, you can play with remote files easily,
without third-party programs others than libcrypto (from OpenSSL).

libssh features:
- Full C library functions for manipulating a client-side SSH connection
- SSH2 protocol compliant
- Fully configurable sessions
- Server support, SSH agent authentication support
- Support for AES-128, AES-192, AES-256, Blowfish, 3DES in CBC mode
- Use multiple SSH connections in a same process, at same time
- Use multiple channels in the same connection
- Thread safety when using different sessions at same time
- POSIX-like SFTP implementation with openssh extension support
- SCP implementation
- RSA and DSS server public key supported
- Compression support (with zlib)
- Public key (RSA and DSS), password and keyboard-interactive authentication

WWW: https://www.libssh.org/