In
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 ...
, an adversary (rarely opponent, enemy) is a malicious entity whose aim is to prevent the users of the
cryptosystem from achieving their goal (primarily
privacy, integrity, and availability of data). An adversary's efforts might take the form of attempting to discover secret data, corrupting some of the data in the system,
spoof
Spoof, spoofs, spoofer, or spoofing may refer to:
* Forgery of goods or documents
* Semen, in Australian slang
* Spoof (game), a guessing game
* Spoofing (finance), a disruptive algorithmic-trading tactic designed to manipulate markets
__NOTOC__ ...
ing the identity of a message sender or receiver, or forcing system downtime.
Actual adversaries, as opposed to idealized ones, are referred to as ''attackers''. The former term predominates in the cryptographic and the latter in the
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, t ...
literature.
Eve, Mallory, Oscar and Trudy are all adversarial characters widely used in both types of texts.
This notion of an adversary helps both intuitive and formal reasoning about cryptosystems by casting security analysis of cryptosystems as a 'game' between the users and a ''centrally co-ordinated'' enemy. The notion of security of a cryptosystem is meaningful only with respect to particular attacks (usually presumed to be carried out by particular sorts of adversaries).
There are several types of adversaries depending on what capabilities or intentions they are presumed to have. Adversaries may be
'Adversary Attacks'
/ref>
* computationally bounded or unbounded (i.e. in terms of time and storage resources),
*eavesdropping or Byzantine (i.e. passively listening on or actively corrupting data in the channel),
*static or adaptive (i.e. having fixed or changing behavior),
*mobile or non-mobile (e.g. in the context of network security
Network security consists of the policies, processes and practices adopted to prevent, detect and monitor unauthorized access, misuse, modification, or denial of a computer network and network-accessible resources. Network security involves th ...
)
and so on. In actual security practice, the attacks assigned to such adversaries are often seen, so such notional analysis is not merely theoretical.
How successful an adversary is at breaking a system is measured by its ''advantage''. An adversary's advantage is the difference between the adversary's probability of breaking the system and the probability that the system can be broken by simply guessing. The advantage is specified as a function of the security parameter
In cryptography, a security parameter is a way of measuring of how "hard" it is for an adversary to break a cryptographic scheme. There are two main types of security parameter: ''computational'' and ''statistical'', often denoted by \kappa and \ ...
.
See also
*Threat model Threat modeling is a process by which potential threats, such as structural vulnerabilities or the absence of appropriate safeguards, can be identified and enumerated, and countermeasures prioritized. The purpose of threat modeling is to provide de ...
*Operations security
Operations security (OPSEC) is a process that identifies critical information to determine if friendly actions can be observed by enemy intelligence, determines if information obtained by adversaries could be interpreted to be useful to them, a ...
References
Cryptographic attacks
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