Comprehensive Guide to Digital Certificates, Security Protocols, and Computer Architecture

Data Items in a Digital Certificate

• Serial Number
• Certificate Authority (CA) that issued the certificate
• CA Digital Signature
• Name of company/organization/individual owning the certificate
• Subject Public Key
• Validity Period of the certificate
• Hashing Algorithm

Conditions for Message Authenticity

• Digital Certificate
• Inclusion of Public Key
• Use of Public Key to hash the received message and produce a message digest
• Comparison of the generated hash to the digital signature

Usage of Encrypted Message Digest

• Financial Transactions
• Legal Documents
• Software Distribution

Process of Digital Signature

1. Software is put through a hashing algorithm.
2. The hash total is encrypted with a private key.
3. The software and encrypted digest hash/digital signature are sent.
4. The receiver possesses the sender's public key.
5. The received hash/digital signature is decrypted with the public key.
6. The receiver hashes the received software.
7. If both hashes match, the software is authentic. OR

1. The CA uses a hashing algorithm to generate a message digest from the particular certificate.
2. The message digest is encrypted with the CA's private key.

Problems SSL and TSL Can Overcome

• Security: For example, alteration of transmitted messages.
• Privacy: For example, ensuring only the intended receiver can view the data.
• Authentication: For example, establishing trust in the other party.

Security Parameters

• Protocol: Which protocol to use.
• Session ID: Uniquely identifies a related series of messages between the server and client.
• Encryption Method: Public or private keys are used by symmetric or asymmetric encryption.
• Authentication Method: Use of digital certificates for authenticity.
• Compression Method: Method to be used for data compression.

Chapter 4: Parallel Processing

Definition

To perform a set of coordinated computations simultaneously in parallel.

Issues with Hardware

Processors need to communicate effectively to transfer processed data.

Issues with Software

• Suitable algorithm/program/software/design.
• Appropriate programming language that allows data processing by multiple processors simultaneously.

Types of Parallel Processing Systems

• Massive: Systems with a large number of processors.
• SISD (Single Instruction Single Data): A computer with only one processor executing one set of instructions on a single set of data. It lacks parallel processing capabilities.
• SIMD (Single Instruction Multiple Data): The processor has several ALUs, each executing the same instruction on different data.
• MIMD (Multiple Instruction Multiple Data): Multiple processors execute different instructions and operate on different data drawn from a common pool.

Chapter 1: Serial File Organization

Reasons for Choosing Serial File Organization

• No need to re-sort data when new data is added.
• Suitable for small files where searching requires minimal processing.
• New records can be easily appended.
• Suitable for batch processing of records.

Types of File Organization

• Sequential: File organized using a unique field, suitable for batch processing where order is not important.
• Random (Direct): Suitable for real-time processing, requires the fastest access to data, and eliminates the need to search through records.

Binary Number Representation

• Binary negative number with the largest magnitude: 10000000 01111111
• Smallest binary positive number: 01000000 00001000
• Decimal equivalent of 0.00195

Chapter 3: Flip-Flops

SR Flip-Flop Instability

When S=0 and R=0, the SR flip-flop produces Q=1 and Q'=1. This is unstable because Q and Q' should be complements of each other.

Advantages of JK Flip-Flop

• All four input combinations are valid.
• The 1-1 combination changes the output to its logical complement.
• Avoids the unstable state present in SR flip-flops.
• Invalid states cannot occur.

Role of Flip-Flops

• Memory and data storage.
• Stores a single bit of information.

Full Adder

• Carry (C): Represents the carry part of the addition of three bits.
• Sum (S): Represents the sum part of the addition of three bits.

Chapter 5: Operating Systems

Process State Transitions

• Blocked to Ready: When an I/O operation completes, a blocked process moves to the ready queue.
• Running to Ready: When a process's time slice expires, an interrupt occurs, and the process transitions to the ready state.
• Termination: When a process finishes execution, it enters the termination state.

Why a Process Cannot Move Directly from Ready to Blocked

A process must initiate an I/O operation to enter a blocked state. I/O operations require the process to be executing, which is only possible in the running state.

Role of Low-Level Scheduler in Multiprogramming OS

• Decides which process from the ready queue should get access to the processor (running state).
• Bases its decision on process priority.
• Invoked after an interrupt or OS call.

Virtual Machine Tasks

• Create and delete virtual machines.
• Make existing hardware available to the guest OS.
• Protect each virtual machine from the actions of other virtual machines.

Difference Between Guest OS and Host OS

• Guest OS: Runs inside a virtual machine and controls virtual hardware.
• Host OS: Controls the physical hardware and runs the virtual machine software.

Uses of Virtual Machines

• Trying out and using alternative operating systems.
• Testing software to identify potential problems.
• Easier to create a VM with a new OS than to set up a new physical computer system.

Limitations of Virtual Machines

• Slower execution speed due to the overhead of running the virtual machine software.
• Difficulty in accurately judging actual response times.
• Challenges in emulating certain hardware components.