Abstract:Blowfish, a new secret-key block cipher, is proposed. It is a Feistel network, iterating a simple encryption function 16 times. The block size is 64 bits, and the key can be any length up to 448 bits. Although there is a complex initialization phase required before any encryption can take place, the actual encryption of data is very efficient on large microprocessors.The cryptographic community needs to provide the world with a new encryption standard. DES [16], the workhorse encryption algorithm for the past fifteen years, is nearing the end of its useful life. Its 56-bit key size is vulnerable to a brute-force attack [22], and recent advances in differential cryptanalysis [1] and linear cryptanalysis [10] indicate that DES is vulnerable to other attacks as well.Many of the other unbroken algorithms in the literature--Khufu [11,12], REDOC II [2,23, 20], and IDEA [7,8,9]--are protected by patents. RC2 and RC4, approved for export with a small key size, are proprietary [18]. GOST [6], a Soviet government algorithm, is specified without the S-boxes. The U.S. government is moving towards secret algorithms, such as the Skipjack algorithm in the Clipper and Capstone chips [17].If the world is to have a secure, unpatented, and freely-available encryption algorithm by the turn of the century, we need to develop several candidate encryption algorithms now. These algorithms can then be subjected to years of public scrutiny and cryptanalysis. Then, the hope is that one or more candidate algorithms will survive this process, and can eventually become a new standard. This paper discusses the requirements for a standard encryption algorithm. While it may not be possible to satisfy all requirements with a single algorithm, it may be possible to satisfy them with a family of algorithms based on the same cryptographic principles.
AREAS OF APPLICATIONA standard encryption algorithm must be suitable for many different applications:Bulk encryption. The algorithm should be efficient in encrypting data files or a continuous data stream.