Custom hardware attack
Encyclopedia
Cryptography
Cryptography is the practice and study of techniques for secure communication in the presence of third parties...
, a custom hardware attack uses specifically designed application-specific integrated circuit
Application-specific integrated circuit
An application-specific integrated circuit is an integrated circuit customized for a particular use, rather than intended for general-purpose use. For example, a chip designed solely to run a cell phone is an ASIC...
s (ASIC) to decipher encrypted messages
Encryption
In cryptography, encryption is the process of transforming information using an algorithm to make it unreadable to anyone except those possessing special knowledge, usually referred to as a key. The result of the process is encrypted information...
.
Mounting a cryptographic brute force attack
Brute force attack
In cryptography, a brute-force attack, or exhaustive key search, is a strategy that can, in theory, be used against any encrypted data. Such an attack might be utilized when it is not possible to take advantage of other weaknesses in an encryption system that would make the task easier...
requires a large number of similar computations: typically trying one key
Key (cryptography)
In cryptography, a key is a piece of information that determines the functional output of a cryptographic algorithm or cipher. Without a key, the algorithm would produce no useful result. In encryption, a key specifies the particular transformation of plaintext into ciphertext, or vice versa...
, checking if the resulting decryption gives a meaningful answer and trying the next key if it does not. Computers can perform these calculations at a rate of millions per second, and thousands of computers can be harnessed together in a distributed computing
Distributed computing
Distributed computing is a field of computer science that studies distributed systems. A distributed system consists of multiple autonomous computers that communicate through a computer network. The computers interact with each other in order to achieve a common goal...
network. But the number of computations required on average grows exponentially
Exponential growth
Exponential growth occurs when the growth rate of a mathematical function is proportional to the function's current value...
with the size of the key and for many problems standard computers are not fast enough. On the other hand, many cryptographic algorithms lend themselves to fast implementation in hardware, i.e. networks of logic circuits or "gates." Integrated circuit
Integrated circuit
An integrated circuit or monolithic integrated circuit is an electronic circuit manufactured by the patterned diffusion of trace elements into the surface of a thin substrate of semiconductor material...
s (ICs) are constructed of these gates and often can execute cryptographic algorithms hundreds of times faster than a general purpose computer.
Each IC can contain large numbers of gates (hundreds of millions in 2005) and the number continues to grow according to Moore's law
Moore's Law
Moore's law describes a long-term trend in the history of computing hardware: the number of transistors that can be placed inexpensively on an integrated circuit doubles approximately every two years....
. Thus the same decryption circuit, or cell, can be replicated thousands of times on one IC. The communications requirements for these ICs are very simple. Each must be initially loaded with a starting point in the key space and, in some situations, with a comparison test value (see known plaintext attack). Output consists of a signal that the IC has found an answer and the successful key.
Since ICs lend themselves to mass production, thousands or even millions of ICs can be applied to a single problem. The ICs themselves can be mounted in printed circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
s. A standard board design can be used for different problems since the communication requirements for the chips are the same. Wafer-scale integration is another possibility. The primary limitations on this method are the cost of chip design
Integrated circuit layout
Integrated circuit layout, also known IC layout, IC mask layout, or mask design, is the representation of an integrated circuit in terms of planar geometric shapes which correspond to the patterns of metal, oxide, or semiconductor layers that make up the components of the integrated circuit.When...
, IC fabrication, floor space, electric power and thermal dissipation.
An alternative approach is to use FPGAs (field-programmable gate array
Field-programmable gate array
A field-programmable gate array is an integrated circuit designed to be configured by the customer or designer after manufacturing—hence "field-programmable"...
s); these are slower and more expensive per gate, but can be reprogrammed for different problems. COPACOBANA (Cost-Optimized Parallel COde Breaker) is such machine, consisting of 120 FPGAs of type Xilinx
Xilinx
Xilinx, Inc. is a supplier of programmable logic devices. It is known for inventing the field programmable gate array and as the first semiconductor company with a fabless manufacturing model....
Spartan3-1000 which run in parallel.
History
The earliest custom hardware attack may have been the BombeBombe
The bombe was an electromechanical device used by British cryptologists to help decipher German Enigma-machine-encrypted signals during World War II...
used to recover Enigma machine
Enigma machine
An Enigma machine is any of a family of related electro-mechanical rotor cipher machines used for the encryption and decryption of secret messages. Enigma was invented by German engineer Arthur Scherbius at the end of World War I...
keys in World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
. In 1998, a custom hardware attack was mounted against the Data Encryption Standard
Data Encryption Standard
The Data Encryption Standard is a block cipher that uses shared secret encryption. It was selected by the National Bureau of Standards as an official Federal Information Processing Standard for the United States in 1976 and which has subsequently enjoyed widespread use internationally. It is...
cipher by the Electronic Frontier Foundation
Electronic Frontier Foundation
The Electronic Frontier Foundation is an international non-profit digital rights advocacy and legal organization based in the United States...
. Their "Deep Crack
EFF DES cracker
In cryptography, the EFF DES cracker is a machine built by the Electronic Frontier Foundation in 1998 to perform a brute force search of DES cipher's key space — that is, to decrypt an encrypted message by trying every possible key...
" machine cost U.S. $250,000 to build and decrypted the DES Challenge II-2
DES Challenges
The DES Challenges were a series of brute force attack contests created by RSA Security for the purpose of highlighting the lack of security provided by the Data Encryption Standard.-The Contests:...
test message after 56 hours of work. The only other confirmed DES cracker was the COPACOBANA machine (Cost-Optimized Parallel COde Breaker) built in 2006. Unlike Deep Crack, COPACOBANA consist of commercially available, reconfigurable integrated circuits. COPACOBANA costs about $10,000 to build and will recover a DES
Data Encryption Standard
The Data Encryption Standard is a block cipher that uses shared secret encryption. It was selected by the National Bureau of Standards as an official Federal Information Processing Standard for the United States in 1976 and which has subsequently enjoyed widespread use internationally. It is...
key in under 6.4 days on average. The cost decrease by roughly a factor of 25 over the EFF machine is an impressive example for the continuous improvement of digital hardware. Adjusting for inflation over 8 years yields an even higher improvement of about 30x. Since 2007, SciEngines GmbH
SciEngines GmbH
SciEngines GmbH is a privately owned company. It has been founded late 2006 as a spin-off of the Universities of Bochum and Kiel, both in Germany. The company has been formed out of the team of the original COPACOBANA project. The project intended to create a platform for an affordable Custom...
, a spin-off company of the two project partners of COPACOBANA has enhanced and developed successors of COPACOBANA. In 2008 their COPACOBANA RIVYERA reduced the time to break DES to the current record of less than one day, using 128 Spartan-3 5000's.. It is generally believed that large government code breaking organizations, such as the U.S. National Security Agency
National Security Agency
The National Security Agency/Central Security Service is a cryptologic intelligence agency of the United States Department of Defense responsible for the collection and analysis of foreign communications and foreign signals intelligence, as well as protecting U.S...
, make extensive use of custom hardware attacks, but no examples have been
declassified
Classified information
Classified information is sensitive information to which access is restricted by law or regulation to particular groups of persons. A formal security clearance is required to handle classified documents or access classified data. The clearance process requires a satisfactory background investigation...
.