MatrixSSL is an embedded SSL and TLS implementation designed for small footprint devices and applications requiring low overhead per connection. The library is less than 50K on disk with cipher suites. It includes SSL and TLS client and server support, session resumption, and implementations of RSA, AES, 3DES, ARC4, SHA1, and MD5. The source is well documented and contains portability layers for additional operating systems, cipher suites, and cryptography providers.
A reasonable way to achieve a long term backup of OpenPGP (GnuPG, PGP, etc) keys is to print them out on paper. Due to metadata and redundancy, OpenPGP secret keys are significantly larger than just the "secret bits". In fact, the secret key contains a complete copy of the public key. Since the public key generally doesn't need to be backed up in this way (most people have many copies of it on various keyservers, Web pages, etc), only extracting the secret parts can be a real advantage. Paperkey extracts just those secret bytes and prints them. To reconstruct, you re-enter those bytes (whether by hand or via OCR), and paperkey can use them to transform your existing public key into a secret key.
John the Ripper is a fast password cracker, currently available for many flavors of Unix, Windows, DOS, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. It supports several crypt(3) password hash types commonly found on Unix systems, as well as Windows LM hashes. On top of this, lots of other hashes and ciphers are added in the community-enhanced version (-jumbo), and some are added in John the Ripper Pro.
GNU SASL is an implementation of the Simple Authentication and Security Layer framework and a few common SASL mechanisms. SASL is used by network servers such as IMAP and SMTP to request authentication from clients, and in clients to authenticate against servers. The library includes support for the SASL framework (with authentication functions and application data privacy and integrity functions) and at least partial support for the CRAM-MD5, EXTERNAL, GSSAPI, ANONYMOUS, PLAIN, SECURID, DIGEST-MD5, LOGIN, NTLM, and KERBEROS_V5 mechanisms.
PolarSSL is a light-weight cryptographic and SSL/TLS library written in C. PolarSSL makes it easy for developers to include cryptographic and SSL/TLS capabilities in their (embedded) applications with as little hassle as possible. Loose coupling of the components inside the library means that it is easy to separate the parts that are needed, without needing to include the total library. PolarSSL is written with embedded systems in mind and has been ported on a number of architectures, including ARM, PowerPC, MIPS, and Motorola 68000. The source is written to have very loose coupling, enabling easy integration of parts in other software projects. Very loosely coupled cryptographic algorithms for MD2, MD4, MD5, SHA1, SHA-256, SHA-512, AES, Camellia, DES, Triple DES, ARC3, and RSA are included.
The stunnel program is designed to work as an SSL encryption wrapper between remote client and local (inetd-startable) or remote server. It can be used to add SSL functionality to commonly used inetd daemons like POP2, POP3, and IMAP servers without any changes in the programs' code. It will negotiate an SSL connection using the OpenSSL or SSLeay libraries. It calls the underlying crypto libraries, so stunnel supports whatever cryptographic algorithms you compiled into your crypto package.
OpenSC provides a set of libraries and utilities to work with smart cards. Its main focus is on cards that support cryptographic operations, and facilitates their use in security applications such as authentication, mail encryption, and digital signatures. OpenSC implements the PKCS#11 API so that applications supporting this API (such as Mozilla Firefox and Thunderbird) can use it. On the card, OpenSC implements the PKCS#15 standard, and aims to be compatible with every software/card that does so.
ACL2 is a mathematical logic, programming language, and mechanical theorem prover based on the applicative subset of Common Lisp. It is an "industrial-strength" version of the NQTHM or Boyer/Moore theorem prover, and has been used for the formal verification of commercial microprocessors, the Java Virtual Machine, interesting algorithms, and so forth.