CISSP Practice

Side channel attacks

Side channel attacks result from the physical implementation of a cryptosystem. Examples of these attacks include timing attacks, power monitoring attacks, TEMPEST attacks, and thermal imaging attacks. Improper error handling in cryptographic operation can also allow side channel attacks. In all these attacks, side channel leakage of information occurs during the physical operation of a cryptosystem through monitoring of sound from computations, observing from a distance, and introducing faults into computations, thus revealing secrets such as the cryptographic key, system-state information, initialization vectors, and plaintext. Side channel attacks are possible even when transmissions between a Web browser and server are encrypted. Note that side channel attacks are different from social engineering attacks where the latter involves deceiving or coercing people who have the legitimate access to a cryptosystem. In other words, the focus of side channel attacks is on data and information, not on people. Countermeasures against the side channel attacks include implementing physical security over hardware, jamming the emitted channel with noise (white noise), designing isochronous software so it runs in a constant amount of time independent of secret values, designing software so that it is PC-secure, building secure CPUs (asynchronous CPUs) so they have no global timing reference, and retransmitting the failed (error prone) transmission with a predetermined number of times.

Sign-off

Functional users are requested and required to approve in writing their acceptance of the system at various stages or phases of the system development life cycle (SDLC).

Signal-to-noise ratio

It is the ratio of the amplitude of the desired signal to the amplitude of noise signals at a given point in time in a telecommunications system. Usually, the signal-to-noise ratio is specified in terms of peak-signal-to-peak-noise ratio, to avoid ambiguity. A low ratio at the receiver is preferred to prevent emanation attack.

Signatory

The entity that generates a digital signature on data using a private key.

Signature

(1) A recognizable, distinguishing pattern associated with an attack, such as a binary string in a virus or a particular set of keystrokes used to gain unauthorized access to a system. (2) A pattern that corresponds to a known threat. (3) The ability to trace the origin of the data.

Signature-based detection

The process of comparing signatures against observed events to identify possible incidents.

Signature certificate

A public key certificate that contains a public key intended for verifying digital signatures rather than encrypting data or performing any other cryptographic functions.

Signature (digital)

A process that operates on a message to assure message source authenticity and integrity, and may be required for source non-repudiation.

Signature generation

The process of using a digital signature algorithm and a private key to generate a digital signature on data. Only the possessor of the user’ private key can perform signature generation.

Signature validation

The mathematical verification of the digital signature and obtaining the appropriate assurances (e.g., public key validity and private key possession).

Signature verification

The process of using a digital signature algorithm and a public key to verify a digital signature. Anyone can verify the signature of a user by employing that user’s public key.

Signed data

The data or message upon which a digital signature has been computed.

Simple mail transfer protocol (SMTP)

It is the most commonly used mail transfer agent (MTA) protocol as defined by IETF RFC 2821. It is the primary protocol used to transfer electronic mail messages on the Internet. SMTP is a host-to-host e-mail protocol. An SMTP server accepts e-mail messages from other systems and stores them for the addressees. It does not provide for reliable authentication and does not require the use of encryption, thus allowing e-mail messages to be easily forged.

Simple Network Management Protocol (SNMP)