JNTU MCA 2019 INFORMATION SECURITY Previous Question Paper (April/May - 2019 - R13)

Security services are processing or communication services provided by a system to give a specific kind of protection to system resources. According to X.800, these include:

• Authentication: Ensures the identity of an entity.
• Access Control: Prevents unauthorized use of resources.
• Data Confidentiality: Protects data from unauthorized disclosure.
• Data Integrity: Ensures data is not altered by unauthorized parties.
• Non-repudiation: Prevents either sender or receiver from denying a transmitted message.

Block ciphers process input data in fixed-size blocks (e.g., 64 or 128 bits). The same key is applied to each block, and the algorithm is generally more complex, making it suitable for bulk data encryption. Examples include AES and DES.

Stream ciphers encrypt data one bit or byte at a time using a continuous stream of pseudorandom bits (keystream) combined with the plaintext via XOR. They are typically faster and require less memory, making them ideal for real-time communication. An example is RC4.