A passive attack on a

cryptosystem In cryptography, a cryptosystem is a suite of cryptographic algorithms needed to implement a particular security service, such as confidentiality (encryption). Typically, a cryptosystem consists of three algorithms: one for key generation, one f ...

is one in which the cryptanalyst cannot interact with any of the parties involved, attempting to break the system solely based upon observed data (i.e. the

ciphertext In cryptography, ciphertext or cyphertext is the result of encryption performed on plaintext using an algorithm, called a cipher. Ciphertext is also known as encrypted or encoded information because it contains a form of the original plaintext ...

). This can also include

known plaintext attack The known-plaintext attack (KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib), and its encrypted version (ciphertext). These can be used to reveal further secret information such as secre ...

s where both the

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 com ...

and its corresponding ciphertext are known. While active attackers can interact with the parties by sending data, a passive attacker is limited to intercepting communications (eavesdropping), and seeks to decrypt data by interpreting the transcripts of authentication sessions. Since passive attackers do not introduce data of their own, they can be difficult to detect. While most classical ciphers are vulnerable to this form of attack, most modern ciphers are designed to prevent this type of attack above all others.

Attributes

*Traffic analysis *Non-evasive

eavesdropping Eavesdropping is the act of secretly or stealthily listening to the private conversation or communications of others without their consent in order to gather information. Etymology The verb ''eavesdrop'' is a back-formation from the noun ''eaves ...

and monitoring of transmissions *Because data unaffected, tricky to detect *Emphasis on prevention (

encryption 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 dec ...

) not detection *Sometimes referred to as "tapping" The main types of passive attacks are traffic analysis and release of message contents. During a traffic analysis attack, the eavesdropper analyzes the traffic, determines the location, identifies communicating hosts and observes the frequency and length of exchanged messages. He uses all this information to predict the nature of communication. All incoming and outgoing traffic of the network is analyzed, but not altered. For a release of message content, a telephonic conversation, an E-mail message or a transferred file may contain confidential data. A passive attack monitors the contents of the transmitted data. Passive attacks are very difficult to detect because they do not involve any alteration of the data. When the messages are exchanged neither the sender nor the receiver is aware that a third party may capture the messages. This can be prevented by encryption of data.

Attributes

See also

References

Further reading