Blowfish is a symmetric block cipher that can be used as a drop-in replacement for DES or IDEA. It takes a variable-length key, from 32 bits to 448 bits, making it ideal for both domestic and exportable use. Blowfish was designed in 1993 by Bruce Schneier as a fast, free alternative to existing encryption algorithms. Since then it has been analyzed considerably, and it is slowly gaining acceptance as a strong encryption algorithm.
The Data Encryption Standard (DES) was developed by an IBM team around 1974 and adopted as a national standard in 1977. Triple DES is a minor variation of this standard. It is three times slower than regular DES but can be billions of times more secure if used properly. Triple DES enjoys much wider use than DES because DES is so easy to break with today's rapidly advancing technology. In 1998 the Electronic Frontier Foundation, using a specially developed computer called the DES Cracker, managed to break DES in less than 3 days. And this was done for under $250,000. The encryption chip that powered the DES Cracker was capable of processing 88 billion keys per second. In addition, it has been shown that for a cost of one million dollars a dedicated hardware device can be built that can search all possible DES keys in about 3.5 hours. This just serves to illustrate that any organization with moderate resources can break through DES with very little effort these days. No sane security expert would consider using DES to protect data.
Triple DES was the answer to many of the shortcomings of DES. Since it is based on the DES algorithm, it is very easy to modify existing software to use Triple DES. It also has the advantage of proven reliability and a longer key length that eliminates many of the shortcut attacks that can be used to reduce the amount of time it takes to break DES. However, even this more powerful version of DES may not be strong enough to protect data for very much longer. The DES algorithm itself has become obsolete and is in need of replacement. To this end the National Institute of Standards and Technology (NIST) is holding a competition to develop the Advanced Encryption Standard (AES) as a replacement for DES. Triple DES has been endorsed by NIST as a temporary standard to be used until the AES is finished sometime in 2001.
The AES will be at least as strong as Triple DES and probably much faster. Many security systems will probably use both Triple DES and AES for at least the next five years. After that, AES may supplant Triple DES as the default algorithm on most systems if it lives up to its expectations. But Triple DES will be kept around for compatibility reasons for many years after that. So the useful lifetime of Triple DES is far from over, even with the AES near completion. For the foreseeable future Triple DES is an excellent and reliable choice for the security needs of highly sensitive information.
In 1972, the National Institute of Standards and Technology (called the National Bureau of Standards at the time) decided that a strong cryptographic algorithm was needed to protect non-classified information. The algorithm was required to be cheap, widely available, and very secure. NIST envisioned something that would be available to the general public and could be used in a wide variety of applications. So they asked for public proposals for such an algorithm. In 1974 IBM submitted the Lucifer algorithm, which appeared to meet most of NIST's design requirements.
NIST enlisted the help of the National Security Agency to evaluate the security of Lucifer. At the time many people distrusted the NSA due to their extremely secretive activities, so there was initially a certain degree of skepticism regarding the analysis of Lucifer. One of the greatest worries was that the key length, originally 128 bits, was reduced to just 56 bits, weakening it significantly. The NSA was also accused of changing the algorithm to plant a "back door" in it that would allow agents to decrypt any information without having to know the encryption key. But these fears proved unjustified and no such back door has ever been found.
The modified Lucifer algorithm was adopted by NIST as a federal standard on November 23, 1976. Its name was changed to the Data Encryption Standard (DES). The algorithm specification was published in January 1977, and with the official backing of the government it became a very widely employed algorithm in a short amount of time.
Unfortunately, over time various shortcut attacks were found that could significantly reduce the amount of time needed to find a DES key by brute force. And as computers became progressively faster and more powerful, it was recognized that a 56-bit key was simply not large enough for high security applications. As a result of these serious flaws, NIST abandoned their official endorsement of DES in 1997 and began work on a replacement, to be called the Advanced Encryption Standard (AES). Despite the growing concerns about its vulnerability, DES is still widely used by financial services and other industries worldwide to protect sensitive on-line applications.
To highlight the need for stronger security than a 56-bit key can offer, RSA Data Security has been sponsoring a series of DES cracking contests since early 1997. In 1998 the Electronic Frontier Foundation won the RSA DES Challenge II-2 contest by breaking DES in less than 3 days. EFF used a specially developed computer called the DES Cracker, which was developed for under $250,000. The encryption chip that powered the DES Cracker was capable of processing 88 billion keys per second. More recently, in early 1999, Distributed. Net used the DES Cracker and a worldwide network of nearly 100,000 PCs to win the RSA DES Challenge III in a record breaking 22 hours and 15 minutes. The DES Cracker and PCs combined were testing 245 billion keys per second when the correct key was found. In addition, it has been shown that for a cost of one million dollars a dedicated hardware device can be built that can search all possible DES keys in about 3.5 hours. This just serves to illustrate that any organization with moderate resources can break through DES with very little effort these days.