The Cryptographic Implementations Analysis Toolkit (CIAT) is a compendium of command line and graphical tools whose aim is to help in the detection and analysis of encrypted byte sequences within files (executable and non-executable). It is particularly helpful in the forensic analysis and reverse engineering of malware using cryptographic code and encrypted payloads.
MonoDecrypt uses pattern matching and its knowledge about character frequencies in order to decrypt messages encoded with a monoalphabetic substitution cipher. MonoDecrypt can decrypt texts of any language, as long as it has sufficient information about the language. Depending on the information you give it, the tool decrypts about 50%-100% on its own. Then you can decrypt the remaining data by filling the gaps or correcting bad guesses. MonoDecrypt can also encrypt texts using monoalphabetic substitution.
cryptod is a program that listens on a TCP port or unix socket, receives information on that port, and performs the requested action. Common actions are aes256 encrypting/decrypting, base64 encoding/decoding, and RMD160 hashing. Interfacing with the daemon is well documented, and you are also easily able to obtain statistics from the server.
ctunnel is a program for tunneling and proxying TCP or UDP connections via a cryptographic tunnel. ctunnel can be used to secure any existing TCP or UDP based protocol, such as HTTP, Telnet, FTP, RSH, MySQL, VNC, DNS, XDMCP, NFS, etc. You can also chain or bounce connections to any number of intermediary hosts.
The Shrew Soft VPN Client for Unix is a free IPsec Client for FreeBSD, NetBSD, and Linux based operating systems. It can be used to communicate with systems running ipsec-tools. The Unix client utilizes the IPsec kernel support included with the operating system, and comes with the complete Internet Key Exchange daemon and client front end application source code. A Windows version is also available.
eurephia is an authentication plug-in for OpenVPN. It enhances the OpenVPN authentication process by using user name and password authentication in addition to SSL certificates. If too many failed attempts are registered, the user account and/or IP address will be blocked. For Linux servers, iptables support is also included, which can be used to restrict each user's network access through the VPN channel. OpenVPN 2.2 or later is required.
The Mandos system allows computers to have encrypted root file systems and at the same time be capable of remote or unattended reboots. The computers run a small client program in the initial RAM disk environment which will communicate with a server over a network. All network communication is encrypted using TLS. The clients are identified by the server using an OpenPGP key that is unique to each client. The server sends the clients an encrypted password. The encrypted password is decrypted by the clients using the same OpenPGP key, and the password is then used to unlock the root file system.