[ Concepts ]
Plaintext
this is the original message which has not yet been encrypted(or an algorithm will applied to).
Ciphertext
This is the encrypted or scrambled message produced by applying the algorithm to the plaintext message using the secret key.
Encryption
The process of scrambling data according to a mathematical formula or algorithm so that the data is unintelligible to all but the intended recipients. In the context of security requirements, encryption enables both privacy (confidentiality of data) and access control (ensuring that the data is accessed only by those who are authorized to do so).
Decryption
The process of descrambling the encoded data to render a secret message intelligible to the intended recipients.
Cryptography
The science of encoding (encrypting) and decoding (decrypting) messages and information in secret code.
Cryptographic algorithm
Key
Formally called cryptographic key, is a sequence of symbols, represented in binary form as a string of bits, which controls the encryption algorithm (the mathematical transformation of plain text into encoded text). The relationship between encrypted messages and their keys is very much like that between locks and keys. Just as a lock can be opened only with the right key, an encrypted message can be decrypted only with the right key. The widely used U.S. Data Encryption Standard (DES) employs a 56-bit key. Generally, the longer the key, the stronger the algorithm.
Strength
One of the main points to make about electronic encryption is there are many qualities, or strengths of it. The systems range from one that's never been broken into and never will be, to encryption that looks scrambled and impenetrable to a novice, but can be broken into by an expert in seconds -- without the use of computers. The strength of encryption technology is determined by the number of bits used in the encryption process. The higher the number of bits used to encrypt, the stronger the encryption technology. For example, IDEA (128-bit key) is stronger than DES (56-bit key). This means that the DES technology would be easier to "crack."
[ How Encryption Works ]
There are two dominant forms of encryption technology that are used all over the world: Symmetric Key Encryption, and Public Key Encryption. Although they work in different ways, they both have the same functional uses.
Symmetric Key Encryption
Public Key Encryption
Practical Uses of the Two Types of Encryption
In practice, Public-Key Encryption (like RSA) is not used to encrypt messages. Public-Key Encryption is secure and convenient, but heavy on computation. Most messages would take a long time to encrypt and decrypt, even with today's computers. Instead, Public-Key Encryption is used as a secure way to send a key for a Symmetric Key Encryption (like DES and IDEA).
Example:
1. you create a file (like an e-mail message).
2. the file is encrypted using symmetric key encryption.
3. The Symmetric Key is encrypted using the receiving computer's Public Key.
4. both encrypted items (file and the Symmetric Key) are sent to the receiving computer.
5. the receiving computer use its private key to decode (decryption) the Symmetric Key.
6. the receiving computer then uses the included symmetric key to decode the original file.
Friday, October 27, 2006
Wednesday, October 04, 2006
computer literacy knowledgebase
data: refers to the symbols that represent facts, objects, and ideas.
information: data becomes information when it is presented in a format that people can understand and use.
stored program: a series of instructions for a computing task can be loaded into a computer's memory.
computer file: usually referred to simply as a file, is a named collection of data that exists on a storage medium, such as a hard disk, floppy disk, or CD.
data file: contains data that can be processed.
executable file: contains the programs or instructions that tell a computer how to perform a specific task.
Application software: is a set of computer program that helps a person carry out a task.
Operating System: is essentially the master controller for all the activities that take place within a computer. Operating system are classified as system software.
What does the OS do?
1. provides a common interface for hardware and software
2. manages processor resources - multi tasking
3. manages memory allocation and protection
4. manages files and storage resources
5. manages system security - file access and desktop access
6. maintains system integrity - error handling
7. provides a user interface.
A process is part of a program
A thread is a separate part of a process
Why multi-user OS?
1. share applications
2. access applications from other computers
3. quickly deply and update applications
binary digits: "bit"
digitize: to convert raw, analog data into digital format represented by 0s and 1s.
Bit: One binary digit./ Byte: 8 bits./ Kilobit: 1,024 or 2(10) bits./ Kilobyte: 1,024 or 2(10) bytes./ Megabit: 1,048,576 or 2(20) bits./ Megabyte: 1,048,576 or 2(20) bytes./ Gigabit: 2(30) bits./ Gigabyte: 2(30) bytes./ Terabyte: 2(40) bytes./ Petabyte: 2(50) bytes./ Exabyte: 2(60) bytes.
integrated circuit: "IC", is a super-thin slice of semiconducting material packed with microscopic circuit elements, such as wires, transistors, capacitors, logic gates, and resistors.
Semiconductor: semiconducting materials such as silicon and germanium, are substances with properties between those of a conductor and an insulator.
binary number system: "base 2", has only two digits 0 and 1 represent numeric data in computer.
microprocessor: is an integrated circuit designed to process instructions.
ALU: arithmetic logic unit, performs arithmetic operations, such as addition and subtraction.
the ALU is responsible for performing arithmetic and logical operations. It use registers to hold data ready to be processed. When it gets the go-ahead signal from the control unit, the ALU processes the data and places the result in an accumulator. From the accumulator, the data can be sent to RAM or used for furhter processing.
registers: ALU uses it to hold data that is being processed.
control unit: fetches each instruction, give the ALU the green light to begin processing.
instruction set: the list of instructions that a microprocessor can perform, are hard-wired into the processor's circuitry and include basic arithmetic and logical operations, fetching data, and clearing registers. a computer can perform very complex tasks, by performing a combination of simple tasks from its instruction set.
Storage device: is the mechanical apparatus that records and retrieves data from a storage medium.
magnetic storage: stores data by magnetizing microscopic particles on the disk or tape surface.
optical storage: store data as microscopic light and dark spots on the disk surface. the dark spots are called pits. the lighter, non-pitted surface areas are called lands.
solid state storage: stores data in a non-volatile, erasable, low-power chip. The chip's circuitry is arranged as a grid and each cell in the grid contain two transistors that act as gates.
Access time: is the average time it takes a computer to locate data on the storage medium and read it. "random access" "sequential access"
Data transfer rate: is the amount of data a stroage device can move per second from the storage medium to the computer.
head crash: if a hard disk read-write head runs into a dust particle or some other contaminant on the disk, it might cause head crash, which damages some of the data on the disk.
Dot pitch: is a measure of image clarity. A smaller dot pitch means a crisper image. Technically, dot pitch is the distance in millimeters between like-colored pixels - the small dots of light that form a an image. a dot pitch between .26 and .23 is typical for today's monitors.
refresh rate: also referred to as vertical scan rate, is the speed at which the screen is repainted.
VGA:640x480 /SVGA:800x600/ XGA:1024x768/ SXGA:1280x1024/ UXGA:1600x1200.
Word size: refers to the number of bits that a microprocessor can manipulate at one time.
programming language: sometimes refered to as computer language provide the tools a programmer uses to create software and produce a lengthy list of instructions, called source code.
machine language: the instruction set that is "hard wired" within the microprocessor's circuits. Therefore, instructions written in a high-level language must be translated into machine language before a computer can use.
compiler: translates all the instructions in a program as a single batch, and the resulting machine language instructions, called object code, are placed in a new file.
interpreter: converts one instruction at a time while the program is running.
application software: provides the computer with instructions for each use to help people carry out tasks using a computer.
system software: operating system, device drivers and utilities - is to help the computer carry out its basic operating functions.
kernel: the core part of the operating system, which provides the most essential operating system services, such as memory management and file access.
Vertical market software: is designed to automate specialized tasks in a specific market or business. examples include patient management and billing software that is specially designed for hospitals, job estimating software for construction business, and student record management software for schools.
Horizontal market software: is generic software that just about any kind of business can use. Payroll software is a good example of horizontal market software.
Groupware: is a type of horizontal market software, designed to help several people collaborate on a single project.
copyright: is a form of legal protection that grants the author of an original "work" an exclusive right to copy, distribute, sell and modify that work, except under special circumstances described by copyright laws.
software license: "license agreement", is a legal contract that defines the ways in which you may use a computer program.
shrink-wrap license: it goes into effect as soon as you open the packaging.
installation agreement: is displayed on-screen when you first install software. After reading the software license on the screen, you can indicate that you accept the terms of the license by clicking a designated button - usually labeled "ok, I agree" or "I accept". if you do not accept the terms, the software does not load and you will not be able to use it.
computer file: or simply file is defined as a named collection of data that exists on a storage medium, such as a disk, CD, DVD, or tape.
application and system files - files that are part of software programs and the operating system.
data files - files that you create yourself using application software.
winxp pro vs home?
1. ability to connect to a windows network
2. enhanced file security (more granular / encryption)
3. built-in webserver
4. remote desktop support
hardware requirement for winxp:
cpu: min. 233mhz, rec. 300+mhz
ram: min. 64mb, rec. 128mb
disk space: 1.5gb
video: svga or higher
cd-rom or dvd drive
network adapter, optional
internet access, optional
why file organizaton?
1. locate your file quickly
2. assign access permissions easily.
3. backup files easily
how?
1. name your file logically and descriptively
2. group files logically and by required permissions
control panel - it provides a central location for modifying how windows xp behaves and looks.
information: data becomes information when it is presented in a format that people can understand and use.
stored program: a series of instructions for a computing task can be loaded into a computer's memory.
computer file: usually referred to simply as a file, is a named collection of data that exists on a storage medium, such as a hard disk, floppy disk, or CD.
data file: contains data that can be processed.
executable file: contains the programs or instructions that tell a computer how to perform a specific task.
Application software: is a set of computer program that helps a person carry out a task.
Operating System: is essentially the master controller for all the activities that take place within a computer. Operating system are classified as system software.
What does the OS do?
1. provides a common interface for hardware and software
2. manages processor resources - multi tasking
3. manages memory allocation and protection
4. manages files and storage resources
5. manages system security - file access and desktop access
6. maintains system integrity - error handling
7. provides a user interface.
A process is part of a program
A thread is a separate part of a process
Why multi-user OS?
1. share applications
2. access applications from other computers
3. quickly deply and update applications
binary digits: "bit"
digitize: to convert raw, analog data into digital format represented by 0s and 1s.
Bit: One binary digit./ Byte: 8 bits./ Kilobit: 1,024 or 2(10) bits./ Kilobyte: 1,024 or 2(10) bytes./ Megabit: 1,048,576 or 2(20) bits./ Megabyte: 1,048,576 or 2(20) bytes./ Gigabit: 2(30) bits./ Gigabyte: 2(30) bytes./ Terabyte: 2(40) bytes./ Petabyte: 2(50) bytes./ Exabyte: 2(60) bytes.
integrated circuit: "IC", is a super-thin slice of semiconducting material packed with microscopic circuit elements, such as wires, transistors, capacitors, logic gates, and resistors.
Semiconductor: semiconducting materials such as silicon and germanium, are substances with properties between those of a conductor and an insulator.
binary number system: "base 2", has only two digits 0 and 1 represent numeric data in computer.
microprocessor: is an integrated circuit designed to process instructions.
ALU: arithmetic logic unit, performs arithmetic operations, such as addition and subtraction.
the ALU is responsible for performing arithmetic and logical operations. It use registers to hold data ready to be processed. When it gets the go-ahead signal from the control unit, the ALU processes the data and places the result in an accumulator. From the accumulator, the data can be sent to RAM or used for furhter processing.
registers: ALU uses it to hold data that is being processed.
control unit: fetches each instruction, give the ALU the green light to begin processing.
instruction set: the list of instructions that a microprocessor can perform, are hard-wired into the processor's circuitry and include basic arithmetic and logical operations, fetching data, and clearing registers. a computer can perform very complex tasks, by performing a combination of simple tasks from its instruction set.
Storage device: is the mechanical apparatus that records and retrieves data from a storage medium.
magnetic storage: stores data by magnetizing microscopic particles on the disk or tape surface.
optical storage: store data as microscopic light and dark spots on the disk surface. the dark spots are called pits. the lighter, non-pitted surface areas are called lands.
solid state storage: stores data in a non-volatile, erasable, low-power chip. The chip's circuitry is arranged as a grid and each cell in the grid contain two transistors that act as gates.
Access time: is the average time it takes a computer to locate data on the storage medium and read it. "random access" "sequential access"
Data transfer rate: is the amount of data a stroage device can move per second from the storage medium to the computer.
head crash: if a hard disk read-write head runs into a dust particle or some other contaminant on the disk, it might cause head crash, which damages some of the data on the disk.
Dot pitch: is a measure of image clarity. A smaller dot pitch means a crisper image. Technically, dot pitch is the distance in millimeters between like-colored pixels - the small dots of light that form a an image. a dot pitch between .26 and .23 is typical for today's monitors.
refresh rate: also referred to as vertical scan rate, is the speed at which the screen is repainted.
VGA:640x480 /SVGA:800x600/ XGA:1024x768/ SXGA:1280x1024/ UXGA:1600x1200.
Word size: refers to the number of bits that a microprocessor can manipulate at one time.
programming language: sometimes refered to as computer language provide the tools a programmer uses to create software and produce a lengthy list of instructions, called source code.
machine language: the instruction set that is "hard wired" within the microprocessor's circuits. Therefore, instructions written in a high-level language must be translated into machine language before a computer can use.
compiler: translates all the instructions in a program as a single batch, and the resulting machine language instructions, called object code, are placed in a new file.
interpreter: converts one instruction at a time while the program is running.
application software: provides the computer with instructions for each use to help people carry out tasks using a computer.
system software: operating system, device drivers and utilities - is to help the computer carry out its basic operating functions.
kernel: the core part of the operating system, which provides the most essential operating system services, such as memory management and file access.
Vertical market software: is designed to automate specialized tasks in a specific market or business. examples include patient management and billing software that is specially designed for hospitals, job estimating software for construction business, and student record management software for schools.
Horizontal market software: is generic software that just about any kind of business can use. Payroll software is a good example of horizontal market software.
Groupware: is a type of horizontal market software, designed to help several people collaborate on a single project.
copyright: is a form of legal protection that grants the author of an original "work" an exclusive right to copy, distribute, sell and modify that work, except under special circumstances described by copyright laws.
software license: "license agreement", is a legal contract that defines the ways in which you may use a computer program.
shrink-wrap license: it goes into effect as soon as you open the packaging.
installation agreement: is displayed on-screen when you first install software. After reading the software license on the screen, you can indicate that you accept the terms of the license by clicking a designated button - usually labeled "ok, I agree" or "I accept". if you do not accept the terms, the software does not load and you will not be able to use it.
computer file: or simply file is defined as a named collection of data that exists on a storage medium, such as a disk, CD, DVD, or tape.
application and system files - files that are part of software programs and the operating system.
data files - files that you create yourself using application software.
winxp pro vs home?
1. ability to connect to a windows network
2. enhanced file security (more granular / encryption)
3. built-in webserver
4. remote desktop support
hardware requirement for winxp:
cpu: min. 233mhz, rec. 300+mhz
ram: min. 64mb, rec. 128mb
disk space: 1.5gb
video: svga or higher
cd-rom or dvd drive
network adapter, optional
internet access, optional
why file organizaton?
1. locate your file quickly
2. assign access permissions easily.
3. backup files easily
how?
1. name your file logically and descriptively
2. group files logically and by required permissions
control panel - it provides a central location for modifying how windows xp behaves and looks.
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