Yarrow algorithm
Encyclopedia
The Yarrow algorithm is a cryptographically secure pseudorandom number generator
. The name is taken from the yarrow
plant, the stalks of which are dried and used as a randomising agent in I Ching divination
.
It was designed by Bruce Schneier
, John Kelsey
, and Niels Ferguson
of Counterpane Labs
(Kelsey et al., 1999). The Yarrow algorithm is explicitly unpatented and royalty-free; no license is required to use it. Yarrow is incorporated in Mac OS X
and FreeBSD
for their /dev/random
devices.
An improved design from Ferguson and Schneier, Fortuna
, is described in their book, Practical Cryptography.
Cryptographically secure pseudorandom number generator
A cryptographically secure pseudo-random number generator is a pseudo-random number generator with properties that make it suitable for use in cryptography.Many aspects of cryptography require random numbers, for example:...
. The name is taken from the yarrow
Yarrow
Achillea millefolium or yarrow is a flowering plant in the family Asteraceae, native to the Northern Hemisphere. In New Mexico and southern Colorado, it is called plumajillo, or "little feather", for the shape of the leaves. In antiquity, yarrow was known as herbal militaris, for its use in...
plant, the stalks of which are dried and used as a randomising agent in I Ching divination
I Ching divination
Among the many forms of divination is a bibliomancy method using the I Ching or Book of Changes. The book is structured as 32 pairs of hexagrams, divided in half after the first 30. The text was a subject for civil service exams in Imperial China...
.
It was designed by Bruce Schneier
Bruce Schneier
Bruce Schneier is an American cryptographer, computer security specialist, and writer. He is the author of several books on general security topics, computer security and cryptography, and is the founder and chief technology officer of BT Managed Security Solutions, formerly Counterpane Internet...
, John Kelsey
John Kelsey (cryptanalyst)
John Kelsey is a cryptographer currently working at NIST. His research interests include cryptanalysis and design of symmetric cryptography primitives , analysis and design of cryptographic protocols, cryptographic random number generation, electronic voting, side-channel attacks on cryptography...
, and Niels Ferguson
Niels Ferguson
Niels T. Ferguson is a Dutch cryptographer and consultant who currently works for Microsoft. He has worked with others, including Bruce Schneier, designing cryptographic algorithms, testing algorithms and protocols, and writing papers and books...
of Counterpane Labs
Counterpane Internet Security
BT Counterpane, formerly Counterpane Internet Security, Inc., is a company that sells managed computer network security services. The company was founded by famous American cryptographer Bruce Schneier in August 1999....
(Kelsey et al., 1999). The Yarrow algorithm is explicitly unpatented and royalty-free; no license is required to use it. Yarrow is incorporated in Mac OS X
Mac OS X
Mac OS X is a series of Unix-based operating systems and graphical user interfaces developed, marketed, and sold by Apple Inc. Since 2002, has been included with all new Macintosh computer systems...
and FreeBSD
FreeBSD
FreeBSD is a free Unix-like operating system descended from AT&T UNIX via BSD UNIX. Although for legal reasons FreeBSD cannot be called “UNIX”, as the direct descendant of BSD UNIX , FreeBSD’s internals and system APIs are UNIX-compliant...
for their /dev/random
/dev/random
In Unix-like operating systems, /dev/random is a special file that serves as a random number generator or as a pseudorandom number generator. It allows access to environmental noise collected from device drivers and other sources. Not all operating systems implement the same semantics for /dev/random...
devices.
An improved design from Ferguson and Schneier, Fortuna
Fortuna (PRNG)
Fortuna is a cryptographically secure pseudorandom number generator devised by Bruce Schneier and Niels Ferguson. It is named after Fortuna, the Roman goddess of chance.- Design :Fortuna is a family of secure PRNGs; its design...
, is described in their book, Practical Cryptography.