cryptography Cryptography, or cryptology (from grc, , translit=kryptós "hidden, secret"; and ''graphein'', "to write", or ''-logia'', "study", respectively), is the practice and study of techniques for secure communication in the presence of adver ...

, SEAL (Software-Optimized Encryption Algorithm) is a stream cipher optimised for machines with a 32-

bit The bit is the most basic unit of information in computing and digital communications. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represente ...

word A word is a basic element of language that carries an objective or practical meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of what a word is, there is no conse ...

size and plenty of

RAM Ram, ram, or RAM may refer to: Animals * A male sheep * Ram cichlid, a freshwater tropical fish People * Ram (given name) * Ram (surname) * Ram (director) (Ramsubramaniam), an Indian Tamil film director * RAM (musician) (born 1974), Dutch * ...

with a reported performance of around 4

cycles per byte Encryption software is software that uses cryptography to prevent unauthorized access to digital information. Cryptography is used to protect digital information on computers as well as the digital information that is sent to other computers over t ...

. SEAL is actually a

pseudorandom function family In cryptography, a pseudorandom function family, abbreviated PRF, is a collection of efficiently-computable functions which emulate a random oracle in the following way: no efficient algorithm can distinguish (with significant advantage) between ...

in that it can easily generate arbitrary portions of the

keystream In cryptography, a keystream is a stream of random or pseudorandom characters that are combined with a plaintext message to produce an encrypted message (the ciphertext). The "characters" in the keystream can be bits, bytes, numbers or actual cha ...

without having to start from the beginning. This makes it particularly well suited for applications like encrypting hard drives. The first version was published by

Phillip Rogaway Phillip Rogaway is a professor of computer science at the University of California, Davis. He graduated from Beverly Hills High School, and later earned a BA in computer science from UC Berkeley and completed his PhD in cryptography at MIT, in t ...

and

Don Coppersmith Don Coppersmith (born 1950) is a cryptographer and mathematician. He was involved in the design of the Data Encryption Standard block cipher at IBM, particularly the design of the S-boxes, strengthening them against differential cryptanalysi ...

in 1994. The current version, published in 1997, is 3.0. SEAL, covered by two patents in the United States, both of which are assigned to IBM.

References

* "Software-efficient pseudorandom function and the use thereof for encryption" * "Computer readable device implementing a software-efficient pseudorandom function encryption" Stream ciphers {{crypto-stub