Data Protection

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Data Protection

• AS Computer Applications
• (2004-2005)

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Aims

• To ensure data is confidential
• No unauthorized access
• e.g. personal info. in computer system
• To ensure data is original
• Data have not been modified by a third party
• e.g. transaction information of on-line banking

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Methods

• User-rights restriction
• Password
• Encryption
• Physical Protection
• Backup

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1. User-rights

• Lets browse the folder Test in the J (student
  drive)
• Lets open the file 123.ppt
• Lets execute the file draw.exe
• Lets delete the file abc.doc

What do you observe?
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1. User-rights

• Lets open the Display Properties window
• Can you find the Setting Tab?

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1. User-rights

• Rules that limit the actions of each user
• Prevent intentional and accidental damage
• Usually 3 user levels
• User
• Power User
• Administrator

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1. User-rights
Administrator Group All modify the rights and
disable accounts of users
Power User Group modify files
User Group Basic read and execute files
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2. Password

• most common way to prevent illegal access

User Name

• Only successful login can enter the system
• A mild way to prevent external damage (e.g.
  hacking)

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2. Password

• Dont let anyone knows your password
• Dont write down password
• Should be changed frequently
• Dont only use number as password
• Dont use passwords which can be easily guessed
• Names
• Birthday
• Words in dictionary

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2. Password
Ahjke84

• What is a good password?

Hard to remember!

• Solution 1 Combine words without space or
  punctuation mark

CANTGUESS
? cant guess
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• Solution 2 Take the first letters from a
  sentence you can easily remember

IASISL
? I Am Studying In Shun Lee

• Solution 3 Mix words and numbers

SMILE497
? both the word smile and the number are
randomly chosen
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3. Encryption

• A message is converted from original to a
  incomprehensible form
• Only the parties involved understand
• Using a key to encrypt and decrypt
• Example

School
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3. Encryption

• Why Encryption?
• User rights restriction password can only
  protect data inside the computer.
• They cant protect data which is being
  transmitted through the computer network

Hello
Hello
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3. Encryption

• Public Key Infrastructure (PKI)
• a comprehensive system of technologies working
  to enable users of the Internet to exchange
  information securely, authenticated and
  confidentially.
• It consists of
• Users key pair (public key private key)
• Digital certificates
• A Certificate Authority

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PKI

• Each user is given a pair of keys

Private Key Public Key

• Using one to lock and the other one to unlock
• The keys are different from real keys
• They are algorithm/programs
• Calculations
• Schemes to decrypt/encrypt messages

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PKI

• Example
• Both Mr. Pau Mr. Kam have applied a Digital
  Certificate
• Each of them will be given a pair of Keys

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PKI

• Private key is kept with the owner
• Public key is kept by the middlemen Certificate
  Authority

Certificate Authority (Hong Kong Post)
K
P
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PKI

• Sending a message (From Mr. Pau to Mr. Kam)

Hi, I am sending you the exam paper
Fdbeh28(!jkjs637chscs012jsakcn_at_

Hi, I am sending you the exam paper
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PKI

• Verifying the owners identity (authentication)

Hi, I am sending you the exam paper
Fdbeh28(!jkjs637chscs012jsakcn_at_

Hi, I am sending you the exam paper
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PKI
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PKI

• Advantages
• Owners keep their private keys
• Private key will not be sent over the Internet
• The private is very safe with the owner
• Certificate Authority
• Middlemen
• Keeping the identity of owners with their public
  keys

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4. Physical Protection

• Locate the computer system in a physically safe
  place
• Protect data from being damaged by sabotage

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5. Backup

• What is backup ?
• A duplicate copy of a file or all files stored in
  a disk.
• Whats the purpose ?
• To protect a system from losing the valuable data
• Backup should be placed at a isolated place

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5. Backup

• Different kinds of backup
• Full backup
• Differential backup
• Incremental backup
• Backup media (Magnetic Tape)
• Cheap
• Reliable

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5. Backup

• Full Backup
• A copy of all records in a information system

identical

• Restoration

Backup
Damaged Database
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5. Backup

• Advantages of full backup
• The safest way of backup
• Simple to backup and restore
• Disadvantages of full backup
• Time consuming
• The system should be offline while making backup

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5. Backup

• Differential Backup
• A supplement of full backup
• Hold the transactions since last backup

Differential Backup
comparing

• Restoration

Differential Backup
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5. Backup

• Incremental Backup
• Hold all transactions

One Transaction

• Restoration

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5. Backup

• Advantages of DB IB
• Small backup file size
• Can be done in a short time(can be done very
  frequently)
• Disadvantages of DB IB
• Restoration is complicated