MEO is a powerful data encryption application to encrypt or decrypt files of any type, including Microsoft Word, email, and PDF documents. It can also create self-extracting encrypted files. This is handy for those who like to view their encrypted files without installing any other encryption software. Also, many downloads supply a checksum or hash value for you to verify the integrity of your download. Meo allows you to create and verify MD5 checksums, SHA-1 hashes, and Tiger Tree hashes.
rfc3394 is a C# implementation of the RFC 3394 key-wrapping algorithm. The associated assembly provides two simple operations: one to wrap key data, and another to unwrap the key data. This code also includes a fairly comprehensive unit test library which, among other things, ensures that the implementation is verified against the test vectors provided in RFC 3394.
tkpg is a program that provides a GUI front end to Philip Zimmermann's Pretty Good Privacy (PGP) public-key encryption system and also the GNU Privacy Guard (GnuPG/gpg) implementation. It utilizes the Clipboard Selection heavily to ease moving pgp-processed text both to and from any of your applications (such as mail reader, news reader, and editor). This removes the need to select the output text by hand or by typing in a filename, since it is usually placed in the Selection automatically for you.
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).
LibRCrypt is an Objective C library for complex data encryption based on Rubik's Cubes. The idea's pretty simple: If you represent data as the squares on a Rubik's Cube, you can apply transformations to the data and get back encrypted data, all of which is commutatitive. Just as a Rubik's Cube can be solved if you know all of the moves, this data can be "unwound", so to speak, if you know all of the transforms applied, but the encryption is even deeper than that. A cube can only cover (9 squares per face x 6 faces) 54 significant bits of data. Therefore, compressed data must be composed of multiple (even thousands) of Rubik's Cubes.
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.