JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III CRYPTOGRAPHY AND NETWORK SECURITY Previous Question Paper (May - 2019 - R16)

A security mechanism is a process, tool, or technique designed to detect, prevent, or recover from a security violation. These mechanisms implement the security policies defined by an organization to protect information assets and communication channels.

Security mechanisms are categorized based on their functional role in protecting system resources:

• Encipherment: The use of mathematical algorithms to transform data into an unreadable format, ensuring confidentiality.
• Digital Signatures: A cryptographic mechanism used to verify the authenticity, integrity, and non-repudiation of digital data.
• Access Control: Procedures that restrict access to system resources based on user identity or authorization levels.
• Data Integrity: Mechanisms such as hash functions or message authentication codes (MACs) that ensure data has not been altered during transmission.
• Authentication Exchange: Protocols designed to verify the identity of an entity, such as passwords, biometrics, or challenge-response mechanisms.
• Traffic Padding: The insertion of dummy data into a communication stream to prevent traffic analysis attacks.
• Routing Control: Selecting secure physical paths for data transmission to avoid compromised network nodes.
• Notarization: The use of a trusted third party to provide evidence regarding the properties of a data exchange, such as time of occurrence or origin.

Steganography is the art and science of hiding the existence of communication by embedding secret data within an innocuous-looking cover medium, such as digital images, audio files, video clips, or text documents. Unlike cryptography, which renders the content of a message unintelligible to unauthorized parties, steganography aims to conceal the very fact that a message is being transmitted.

The fundamental components of a steganographic system include:

• Cover Object: The original, non-secret file used to host the hidden data.
• Secret Message: The data that the sender intends to conceal.
• Stego-Object: The final file produced after the secret message has been embedded into the cover object.
• Stego-Key: An optional secret parameter used to control the embedding process, ensuring that only a recipient with the key can extract the hidden information.

Common techniques include Least Significant Bit (LSB) insertion, where the least significant bits of pixels in an image are replaced with bits of the secret message. Because the change to the pixel value is minimal, the human eye cannot perceive the difference between the original cover object and the stego-object. The primary goal is to maintain imperceptibility, ensuring that the statistical properties of the cover medium remain largely unchanged to evade detection by steganalysis tools.