Botan is a crypto library written in C++. It provides a variety of cryptographic algorithms, including common ones such as AES, MD5, SHA, HMAC, RSA, Diffie-Hellman, DSA, and ECDSA, as well as many others that are more obscure or specialized. It also offers SSL/TLS (client and server), X.509v3 certificates and CRLs, and PKCS #10 certificate requests. A message processing system that uses a filter/pipeline metaphor allows for many common cryptographic tasks to be completed with just a few lines of code. Assembly and SIMD optimizations for common CPUs offers speedups for critical algorithms like AES and SHA-1.
MpNT is a multi-precision number theory library that provides a base for building cryptographic applications. It may also be used in any other domain where efficient large number computations are required. The library supports integer, modular, and floating point arithmetic with practically unlimited precision. It is both speed efficient and highly portable without disregarding code structure and clarity.
NetCrack is cluster software developed to distribute a hashing algorithm's cracking process work using a brute force attack. Currently, it only supports the two most commonly used hashing algorithms: MD5 and SHA-1. Support is included for MySQL, safe mode, and others. It works like a client/server application, where the server is unique for each cluster network and its job is to distribute the cracking process work, coordinate the nodes, and prevent connections and data integrity errors.
PyCryptoPlus is a cryptographic module similar to PyCrypto, with which it shares the API. But PyCryptoPlus is written 100% in Python, so its primary interest is educational and scientific; if you want real speed, you're better checking out PyCrypto. It was not completely written from scratch, but integrates other cipher codes when available in Python and under appropriate licenses. It contains, among other things: Block cipher algorithms (Serpent, Blowfish, Twofish, DES, 3DES, AES, Rijndael, and PRESENT); modes of operation (CMAC, ECB, CBC, CTR, and XTS); paddings (bit padding, zeros, PKCS7, PKCS12, ISO 10126, and ANSI X.923); and one-way functions (MD5, SHA1/SHA2, Whirlpool, RipeMD, RadioGatun, HMAC, and PBKDF2).
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.
Bitcoin is a peer-to-peer electronic cash system that is completely decentralized, without the need for a central server or trusted parties. Users hold the crypto keys to their own money and transact directly with each other, with the help of a P2P network to check for double-spending.
DeleGate is a multi-purpose application level gateway or proxy server that mediates communication of various protocols, applying cache and conversion for mediated data, controlling access from clients, and routing toward servers. It translates protocols between clients and servers, converting between IPv4 and IPv6, applying SSL (TLS) to arbitrary protocols, merging several servers into a single server view with aliasing and filtering. It can be used as a simple origin server for some protocols (HTTP, FTP, and NNTP).
Open Transactions is a solid, easy-to-use, financial crypto and digital cash library, including an API, server, and test client. It features anonymous numbered accounts, untraceable digital cash, triple-signed receipts, basket currencies, and signed XML contracts. It also supports cheques, invoices, payment plans, markets with trades, and other instruments. It uses OpenSSL and Lucre blinded tokens.