HOME

TheInfoList



OR:

In
computer security Computer security, cybersecurity (cyber security), or information technology security (IT security) is the protection of computer systems and networks from attack by malicious actors that may result in unauthorized information disclosure, the ...
, a side-channel attack is any attack based on extra information that can be gathered because of the fundamental way a
computer protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...
or
algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...
is implemented, rather than flaws in the design of the protocol or algorithm itself (e.g. flaws found in a
cryptanalysis Cryptanalysis (from the Greek ''kryptós'', "hidden", and ''analýein'', "to analyze") refers to the process of analyzing information systems in order to understand hidden aspects of the systems. Cryptanalysis is used to breach cryptographic sec ...
of a
cryptographic algorithm In cryptography, encryption is the process of encoding information. This process converts the original representation of the information, known as plaintext, into an alternative form known as ciphertext. Ideally, only authorized parties can decip ...
) or minor, but potentially devastating, mistakes or oversights in the implementation. (Cryptanalysis also includes searching for side-channel attacks.) Timing information, power consumption,
electromagnetic In physics, electromagnetism is an interaction that occurs between particles with electric charge. It is the second-strongest of the four fundamental interactions, after the strong force, and it is the dominant force in the interactions of a ...
leaks, and
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by the ...
are examples of extra information which could be exploited to facilitate side-channel attacks. Some side-channel attacks require technical knowledge of the internal operation of the system, although others such as
differential power analysis Power analysis is a form of side channel attack in which the attacker studies the power consumption of a cryptographic hardware device. These attacks rely on basic physical properties of the device: semiconductor devices are governed by the l ...
are effective as
black-box In science, computing, and engineering, a black box is a system which can be viewed in terms of its inputs and outputs (or transfer characteristics), without any knowledge of its internal workings. Its implementation is "opaque" (black). The te ...
attacks. The rise of
Web 2.0 Web 2.0 (also known as participative (or participatory) web and social web) refers to websites that emphasize user-generated content, ease of use, participatory culture and interoperability (i.e., compatibility with other products, systems, and ...
applications and
software-as-a-service Software as a service (SaaS ) is a software licensing and delivery model in which software is licensed on a subscription basis and is centrally hosted. SaaS is also known as "on-demand software" and Web-based/Web-hosted software. SaaS is cons ...
has also significantly raised the possibility of side-channel attacks on the web, even when transmissions between a web browser and server are encrypted (e.g. through
HTTPS Hypertext Transfer Protocol Secure (HTTPS) is an extension of the Hypertext Transfer Protocol (HTTP). It is used for secure communication over a computer network, and is widely used on the Internet. In HTTPS, the communication protocol is enc ...
or
WiFi Wi-Fi () is a family of wireless network protocols, based on the IEEE 802.11 family of standards, which are commonly used for local area networking of devices and Internet access, allowing nearby digital devices to exchange data by radio waves ...
encryption), according to researchers from
Microsoft Research Microsoft Research (MSR) is the research subsidiary of Microsoft. It was created in 1991 by Richard Rashid, Bill Gates and Nathan Myhrvold with the intent to advance state-of-the-art computing and solve difficult world problems through technologi ...
and
Indiana University Indiana University (IU) is a system of public universities in the U.S. state of Indiana. Campuses Indiana University has two core campuses, five regional campuses, and two regional centers under the administration of IUPUI. *Indiana Universit ...
. Many powerful side-channel attacks are based on statistical methods pioneered by Paul Kocher. Attempts to break a cryptosystem by deceiving or coercing people with legitimate access are not typically considered side-channel attacks: see
social engineering Social engineering may refer to: * Social engineering (political science), a means of influencing particular attitudes and social behaviors on a large scale * Social engineering (security), obtaining confidential information by manipulating and/or ...
and
rubber-hose cryptanalysis In cryptography, rubber-hose cryptanalysis is a euphemism for the extraction of cryptographic secrets (e.g. the password to an encrypted file) from a person by coercion or torture—such as beating that person with a rubber hose, hence the na ...
. General classes of side-channel attack include: * Cache attack — attacks based on attacker's ability to monitor cache accesses made by the victim in a shared physical system as in virtualized environment or a type of cloud service. *
Timing attack In cryptography, a timing attack is a side-channel attack in which the attacker attempts to compromise a cryptosystem by analyzing the time taken to execute cryptographic algorithms. Every logical operation in a computer takes time to execute, and ...
— attacks based on measuring how much time various computations (such as, say, comparing an attacker's given password with the victim's unknown one) take to perform. * Power-monitoring attack — attacks that make use of varying power consumption by the hardware during computation. *
Electromagnetic attack In cryptography, electromagnetic attacks are side-channel attacks performed by measuring the electromagnetic radiation emitted from a device and performing signal analysis on it. These attacks are a more specific type of what is sometimes referred ...
— attacks based on leaked electromagnetic radiation, which can directly provide plaintexts and other information. Such measurements can be used to infer cryptographic keys using techniques equivalent to those in power analysis or can be used in non-cryptographic attacks, e.g.
TEMPEST Tempest is a synonym for a storm. '' The Tempest'' is a play by William Shakespeare. Tempest or The Tempest may also refer to: Arts and entertainment Films * ''The Tempest'' (1908 film), a British silent film * ''The Tempest'' (1911 film), a ...
(aka
van Eck phreaking Van Eck phreaking, also known as Van Eck radiation, is a form of eavesdropping in which special equipment is used to pick up side-band electromagnetic emissions from electronic devices that correlate to hidden signals or data to recreate these sig ...
or radiation monitoring) attacks. *
Acoustic cryptanalysis Acoustic cryptanalysis is a type of side channel attack that exploits sounds emitted by computers or other devices. Most of the modern acoustic cryptanalysis focuses on the sounds produced by computer keyboards and internal computer components, bu ...
— attacks that exploit sound produced during a computation (rather like power analysis). * Differential fault analysis — in which secrets are discovered by introducing faults in a computation. *
Data remanence Data remanence is the residual representation of digital data that remains even after attempts have been made to remove or erase the data. This residue may result from data being left intact by a nominal file deletion operation, by reformatting o ...
— in which sensitive data are read after supposedly having been deleted. (e.g.
Cold boot attack In computer security, a cold boot attack (or to a lesser extent, a platform reset attack) is a type of side channel attack in which an attacker with physical access to a computer performs a memory dump of a computer's random-access memory (RAM) by ...
) * Software-initiated fault attacks — Currently a rare class of side channels,
Row hammer Row hammer (also written as rowhammer) is a security exploit that takes advantage of an unintended and undesirable side effect in dynamic random-access memory (DRAM) in which memory cells interact electrically between themselves by leaking thei ...
is an example in which off-limits memory can be changed by accessing adjacent memory too often (causing state retention loss). * Allowlist — attacks based on the fact that the allowlisting devices will behave differently when communicating with allowlisted (sending back the responses) and non-allowlisted (not responding to the devices at all) devices. Allowlist-based side channel may be used to track Bluetooth MAC addresses. * Optical - in which secrets and sensitive data can be read by visual recording using a high resolution camera, or other devices that have such capabilities (see examples below). In all cases, the underlying principle is that physical effects caused by the operation of a cryptosystem (''on the side'') can provide useful extra information about secrets in the system, for example, the
cryptographic key A key in cryptography is a piece of information, usually a string of numbers or letters that are stored in a file, which, when processed through a cryptographic algorithm, can encode or decode cryptographic data. Based on the used method, the key c ...
, partial state information, full or partial
plaintext In cryptography, plaintext usually means unencrypted information pending input into cryptographic algorithms, usually encryption algorithms. This usually refers to data that is transmitted or stored unencrypted. Overview With the advent of comp ...
s and so forth. The term cryptophthora (secret degradation) is sometimes used to express the degradation of secret key material resulting from side-channel leakage.


Examples

A works by monitoring security critical operations such as AES T-table entry or modular exponentiation or multiplication or memory accesses. The attacker then is able to recover the secret key depending on the accesses made (or not made) by the victim, deducing the encryption key. Also, unlike some of the other side-channel attacks, this method does not create a fault in the ongoing cryptographic operation and is invisible to the victim. In 2017, two CPU vulnerabilities (dubbed
Meltdown Meltdown may refer to: Science and technology * Nuclear meltdown, a severe nuclear reactor accident * Meltdown (security vulnerability), affecting computer processors * Mutational meltdown, in population genetics Arts and entertainment Music * Me ...
and
Spectre Spectre, specter or the spectre may refer to: Religion and spirituality * Vision (spirituality) * Apparitional experience * Ghost Arts and entertainment Film and television * ''Spectre'' (1977 film), a made-for-television film produced and writ ...
) were discovered, which can use a cache-based side channel to allow an attacker to leak memory contents of other processes and the operating system itself. A timing attack watches data movement into and out of the CPU or memory on the hardware running the cryptosystem or algorithm. Simply by observing variations in how long it takes to perform cryptographic operations, it might be possible to determine the entire secret key. Such attacks involve statistical analysis of timing measurements and have been demonstrated across networks. A power-analysis attack can provide even more detailed information by observing the power consumption of a hardware device such as CPU or cryptographic circuit. These attacks are roughly categorized into simple power analysis (SPA) and differential power analysis (DPA). Example of machine learning approaches are in. Fluctuations in current also generate
radio waves Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz (GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (short ...
, enabling attacks that analyze measurements of electromagnetic (EM) emanations. These attacks typically involve similar statistical techniques as power-analysis attacks. A deep-learning-based side-channel attack, using the power and EM information across multiple devices has been demonstrated with the potential to break the secret key of a different but identical device in as low as a single trace. Historical analogues to modern side-channel attacks are known. A recently declassified NSA document reveals that as far back as 1943, an engineer with
Bell telephone The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over one hundre ...
observed decipherable spikes on an oscilloscope associated with the decrypted output of a certain encrypting teletype. According to former
MI5 The Security Service, also known as MI5 ( Military Intelligence, Section 5), is the United Kingdom's domestic counter-intelligence and security agency and is part of its intelligence machinery alongside the Secret Intelligence Service (MI6), Go ...
officer Peter Wright, the British Security Service analyzed emissions from French cipher equipment in the 1960s. In the 1980s,
Soviet The Soviet Union,. officially the Union of Soviet Socialist Republics. (USSR),. was a List of former transcontinental countries#Since 1700, transcontinental country that spanned much of Eurasia from 1922 to 1991. A flagship communist state, ...
eavesdroppers were suspected of having planted bugs inside IBM
Selectric The IBM Selectric typewriter was a highly successful line of electric typewriters introduced by IBM on 31 July 1961. Instead of the "basket" of individual typebars that swung up to strike the ribbon and page in a typical typewriter of the perio ...
typewriters to monitor the electrical noise generated as the type ball rotated and pitched to strike the paper; the characteristics of those signals could determine which key was pressed. Power consumption of devices causes heating, which is offset by cooling effects. Temperature changes create thermally induced mechanical stress. This stress can create low level acoustic emissions from operating CPUs (about 10 kHz in some cases). Recent research by Shamir et al. has suggested that information about the operation of cryptosystems and algorithms can be obtained in this way as well. This is an acoustic cryptanalysis attack. If the surface of the CPU chip, or in some cases the CPU package, can be observed,
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
images can also provide information about the code being executed on the CPU, known as a thermal-imaging attack. An optical side-channel attack examples include gleaning information from the hard disk activity indicator to reading a small number of photons emitted by transistors as they change state. Allocation-based side channels also exist and refer to the information that leaks from the allocation (as opposed to the use) of a resource such as network bandwidth to clients that are concurrently requesting the contended resource.


Countermeasures

Because side-channel attacks rely on the relationship between information emitted (leaked) through a side channel and the secret data, countermeasures fall into two main categories: (1) eliminate or reduce the release of such information and (2) eliminate the relationship between the leaked information and the secret data, that is, make the leaked information unrelated, or rather ''uncorrelated'', to the secret data, typically through some form of randomization of the ciphertext that transforms the data in a way that can be undone after the cryptographic operation (e.g., decryption) is completed. Under the first category, displays with special shielding to lessen electromagnetic emissions, reducing susceptibility to
TEMPEST Tempest is a synonym for a storm. '' The Tempest'' is a play by William Shakespeare. Tempest or The Tempest may also refer to: Arts and entertainment Films * ''The Tempest'' (1908 film), a British silent film * ''The Tempest'' (1911 film), a ...
attacks, are now commercially available. Power line conditioning and filtering can help deter power-monitoring attacks, although such measures must be used cautiously, since even very small correlations can remain and compromise security. Physical enclosures can reduce the risk of surreptitious installation of microphones (to counter acoustic attacks) and other micro-monitoring devices (against CPU power-draw or thermal-imaging attacks). Another countermeasure (still in the first category) is to jam the emitted channel with noise. For instance, a random delay can be added to deter timing attacks, although adversaries can compensate for these delays by averaging multiple measurements (or, more generally, using more measurements in the analysis). When the amount of noise in the side channel increases, the adversary needs to collect more measurements. Another countermeasure under the first category is to use security analysis software to identify certain classes of side-channel attacks that can be found during the design stages of the underlying hardware itself. Timing attacks and cache attacks are both identifiable through certain commercially available security analysis software platforms, which allow for testing to identify the attack vulnerability itself, as well as the effectiveness of the architectural change to circumvent the vulnerability. The most comprehensive method to employ this countermeasure is to create a Secure Development Lifecycle for hardware, which includes utilizing all available security analysis platforms at their respective stages of the hardware development lifecycle. In the case of timing attacks against targets whose computation times are quantized into discrete clock cycle counts, an effective countermeasure against is to design the software to be isochronous, that is to run in an exactly constant amount of time, independently of secret values. This makes timing attacks impossible."A Network-based Asynchronous Architecture for Cryptographic Devices"
by Ljiljana Spadavecchia 2005 in sections "3.2.3 Countermeasures", "3.4.2 Countermeasures", "3.5.6 Countermeasures", "3.5.7 Software countermeasures", "3.5.8 Hardware countermeasures", and "4.10 Side-channel analysis of asynchronous architectures".
Such countermeasures can be difficult to implement in practice, since even individual instructions can have variable timing on some CPUs. One partial countermeasure against simple power attacks, but not differential power-analysis attacks, is to design the software so that it is "PC-secure" in the "program counter security model". In a PC-secure program, the execution path does not depend on secret values. In other words, all conditional branches depend only on public information. (This is a more restrictive condition than isochronous code, but a less restrictive condition than branch-free code.) Even though multiply operations draw more power than NOP on practically all CPUs, using a constant execution path prevents such operation-dependent power differences (differences in power from choosing one branch over another) from leaking any secret information. On architectures where the instruction execution time is not data-dependent, a PC-secure program is also immune to timing attacks. Another way in which code can be non-isochronous is that modern CPUs have a memory cache: accessing infrequently used information incurs a large timing penalty, revealing some information about the frequency of use of memory blocks. Cryptographic code designed to resist cache attacks attempts to use memory in only a predictable fashion (like accessing only the input, outputs and program data, and doing so according to a fixed pattern). For example, data-dependent table lookups must be avoided because the cache could reveal which part of the lookup table was accessed. Other partial countermeasures attempt to reduce the amount of information leaked from data-dependent power differences. Some operations use power that is correlated to the number of 1 bits in a secret value. Using a
constant-weight code In coding theory, a constant-weight code, also called an ''m''-of-''n'' code, is an error detection and correction code where all codewords share the same Hamming weight. The one-hot code and the balanced code are two widely used kinds of constan ...
(such as using
Fredkin gate The Fredkin gate (also CSWAP gate and conservative logic gate) is a computational circuit suitable for reversible computing, invented by Edward Fredkin. It is ''universal'', which means that any logical or arithmetic operation can be constructed en ...
s or dual-rail encoding) can reduce the leakage of information about the
Hamming weight The Hamming weight of a string is the number of symbols that are different from the zero-symbol of the alphabet used. It is thus equivalent to the Hamming distance from the all-zero string of the same length. For the most typical case, a string o ...
of the secret value, although exploitable correlations are likely to remain unless the balancing is perfect. This "balanced design" can be approximated in software by manipulating both the data and its complement together. Several "secure CPUs" have been built as
asynchronous CPU Asynchronous circuit (clockless or self-timed circuit) is a sequential digital logic circuit that does not use a global clock circuit or signal generator to synchronize its components. Instead, the components are driven by a handshaking circu ...
s; they have no global timing reference. While these CPUs were intended to make timing and power attacks more difficult, subsequent research found that timing variations in asynchronous circuits are harder to remove. A typical example of the second category (decorrelation) is a technique known as '' blinding''. In the case of RSA decryption with secret exponent d and corresponding encryption exponent e and modulus m, the technique applies as follows (for simplicity, the modular reduction by ''m'' is omitted in the formulas): before decrypting, that is, before computing the result of y^d for a given ciphertext y, the system picks a random number r and encrypts it with public exponent e to obtain r^e. Then, the decryption is done on y \cdot r^e to obtain ^d = y^d \cdot r^ = y^d \cdot r. Since the decrypting system chose r, it can compute its inverse modulo m to cancel out the factor r in the result and obtain y^d, the actual result of the decryption. For attacks that require collecting side-channel information from operations with data ''controlled by the attacker'', blinding is an effective countermeasure, since the actual operation is executed on a randomized version of the data, over which the attacker has no control or even knowledge. A more general countermeasure (in that it is effective against all side-channel attacks) is the masking countermeasure. The principle of masking is to avoid manipulating any sensitive value y directly, but rather manipulate a sharing of it: a set of variables (called "shares") y_1, ..., y_d such that y = y_1 \oplus ... \oplus y_d (where \oplus is the
XOR Exclusive or or exclusive disjunction is a logical operation that is true if and only if its arguments differ (one is true, the other is false). It is symbolized by the prefix operator J and by the infix operators XOR ( or ), EOR, EXOR, , ...
operation). An attacker must recover all the values of the shares to get any meaningful information. Recently, white-box modeling was utilized to develop a low-overhead generic circuit-level countermeasure against both EM as well as power side-channel attacks. To minimize the effects of the higher-level metal layers in an IC acting as more efficient antennas, the idea is to embed the crypto core with a signature suppression circuit,"High efficiency power side-channel attack immunity using noise injection in attenuated signature domain"
by D. Das, S. Maity, S.B. Nasir, S. Ghosh, A. Raychowdhury and S. Sen, in IEEE International Symposium on Hardware Oriented Security and Trust (HOST), Washington, DC, 2017.
routed locally within the lower-level metal layers, leading towards both power and EM side-channel attack immunity.


See also

*
Brute-force attack In cryptography, a brute-force attack consists of an attacker submitting many passwords or passphrases with the hope of eventually guessing correctly. The attacker systematically checks all possible passwords and passphrases until the correct ...
*
Computer and network surveillance Computer and network surveillance is the monitoring of computer activity and data stored locally on a computer or data being transferred over computer networks such as the Internet. This monitoring is often carried out covertly and may be comple ...
*
Covert channel In computer security, a covert channel is a type of attack that creates a capability to transfer information objects between processes that are not supposed to be allowed to communicate by the computer security policy. The term, originated in 197 ...
*
Side effect In medicine, a side effect is an effect, whether therapeutic or adverse, that is secondary to the one intended; although the term is predominantly employed to describe adverse effects, it can also apply to beneficial, but unintended, consequence ...


References


Further reading


Books

*


Articles



Differential Power Analysis, P. Kocher, J. Jaffe, B. Jun, appeared in CRYPTO'99.

Side channel attack: an approach based on machine learning, 2011, L Lerman, G Bontempi, O Markowitch.

Timing Attacks on Implementations of Diffie-Hellman, RSA, DSS, and Other Systems, P. Kocher.

Introduction to Differential Power Analysis and Related attacks, 1998, P Kocher, J Jaffe, B Jun.
Nist.gov
a cautionary Note Regarding Evaluation of AES Candidates on Smart Cards, 1999, S Chari, C Jutla, J R Rao, P Rohatgi * DES and Differential Power Analysis, L Goubin and J Patarin, in Proceedings of CHES'99, Lecture Notes in Computer Science Nr 1717, Springer-Verlag * * *


External links

* Sima, Mihai; Brisson, André (2015)
Whitenoise Encryption Implementation with Increased Robustness against Side-Channel Attacks
* Brisson, André (2015
University of Victoria, British Columbia Side Channel Attack Resistance study of Whitenoise

New side channel attack techniques

COSADE Workshop
International Workshop on Constructive Side-Channel Analysis and Secure Design {{DEFAULTSORT:Side Channel Attack Cryptographic attacks