In cryptography

Cryptography

Cryptography is the practice and study of techniques for secure communication in the presence of third parties...

, SEAL (Software-Optimized Encryption Algorithm) is a very fast stream cipher

Stream cipher

In cryptography, a stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream . In a stream cipher the plaintext digits are encrypted one at a time, and the transformation of successive digits varies during the encryption...

 optimised for machines with a 32-bit

Bit

A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

 word

Word

In language, a word is the smallest free form that may be uttered in isolation with semantic or pragmatic content . This contrasts with a morpheme, which is the smallest unit of meaning but will not necessarily stand on its own...

 size and plenty of RAM. SEAL is actually a pseudorandom function family in that it can easily generate arbitrary portions of the keystream

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 ....

 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

Phillip Rogaway is a professor of computer science at the University of California, Davis. He graduated with an BA in computer science from UC Berkeley and completed his PhD in cryptography at MIT, in the Theory of Computation group. He has taught at UC Davis since 1994.Dr...

 and Don Coppersmith

Don Coppersmith

Don Coppersmith 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 cryptanalysis...

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

IBM

International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...

.