■<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=unicode"> <meta http-equiv="Content-Language" content="en-us"> <title>Cobian Backup 8 - Compression and Encryption</title> <link rel="stylesheet" type="text/css" href="CobStyle.css"> </head> <body> <div align="center"> <table border="0" width="600" id="table1"> <tr> <td> Compression and encryption Cobian Backup 8 uses two methods of compression: the standard Zip format or the SQX method. The standard zip format has restrictions about the size and the quantity of files that an archive can handle. If the archive gets large enough Cobian Backup 8 will automatically use Zip64. This is a new enhanced format that will handle huge  archives and is compatible with the last version of PKWARE's PKZip. You can also create archives in "Blocked" mode. In this case, the archive will be split into blocks. This is useful if you wish then to copy the archive into removable media such as CDs. The SQX format has the advantage of having a better compression than ZIP. This method can use different algorithms of compression for different types of files, thus resulting in a more optimal compression of the archive. SQX offers also the possibility of using a piece of the file or an external file to store redundant data to make possible the restoring of a damaged archive. Cobian Backup 8 can use strong encryption to protect your files. You can set a passphrase into the <a href="tasks_en.htm">Task dialog box</a> and then you can use one of four  methods to encrypt: RSA-Rijndael - This combined method encrypts the file using the Rijndael method (see further) using a RANDOMLY created 256-bits key. This key is then asymmetrically encrypted with a public 1024-bit RSA key and embedded into the resulting file. To decrypt a file that has been encrypting using this method, you need to use the private key. You can create a RSA key pair using the Decrypting tool in the Tool menu. Blowfish: Bruce Schneier designed Blowfish in 1993. It is a symmetric block cipher with key lengths from 32 bits to 448 bits (Cobian Backup 8 implementation uses a 128 bits key).The algorithm is patent, royalty and license free. Since its introduction, Blowfish has been extensively analyzed, with papers being published by many cryptographers. It is acknowledged as a strong cipher, especially with the recommended number of rounds. There have been attacks and weaknesses published on using Blowfish with fewer rounds, but note that Cobian Backup 8 implements the recommended number and so doesn t suffer from these problems. Rijndael: The Rijndael encryption algorithm was the finalist in the Advanced Encryption Standard (AES) selection process run by the National Institute of Standards and Technology (NIST). Two Belgian cryptographers, Joan Daemen and Vincent Rijmen, devised Rijndael for the AES competition in 1998. It is a symmetric block cipher with variable key lengths and block sizes. In their paper, the authors promoted key lengths of 128, 192, and 256 bits, with block sizes of 128, 192, and 256 bits. Cobian Backup 8 supports 128 bit keys and 128-bit blocks. Rijndael (pronounced "Rhine Dahl") is interesting from a cryptographic viewpoint as, unlike many of the ciphers invented since DES, is it not a Feistal cipher. DES: The Data Encryption Standard (DES) algorithm was the first encryption standard. It was adopted as a federal standard in 1976. IBM proposed the algorithm to the National Bureau of Standards (the precursor of the National Institute of Standards and Technology) based upon an earlier algorithm called LUCIFER. The National Security Agency refined some internal aspects of the algorithm during a review process. The algorithm is free of royalties and licenses. DES is a symmetric block cipher. The key length is usually quoted as 64 bits, but in reality only 56 bits of these 64 participate in the encryption algorithm. The other eight bits are parity or check bits and are stripped prior to the encryption or decryption process. The block size is 64 bits (8 bytes).During its acceptance phase, DES was extensively analyzed and is now accepted to be a strong algorithm, except for one area: the key length. A 56-bit key is within the reach of brute-force attacks using a network of high-powered machines. DES should therefore only be used for temporary data; data that would be out-of-date before someone brute-force cracked an encrypted message or data that doesn't need a very strong encryption. Please note that encryption can be a VERY lengthy operation for large files.<a href="index_en.htm">Index</a></td> </tr> <tr> <td> ⌐2000-2006 by Luis Cobian All rights reserved</td> </tr> </table> </div> </body> </html>