6.2 SecurityPrivacy&DataIntegrity.data_integrity Flashcards
What is data integrity?
Data integrity refers to the accuracy, completeness, and consistency of data.
How can data integrity be compromised?
- During data entry and data transmission.
- By malicious attacks like malware or hacking.
- Through accidental data loss from hardware issues.
What are two methods used to ensure data integrity?
Validation and verification.
What is validation?
A method used to ensure entered data is reasonable and meets specific input criteria.
What is verification?
A method used to ensure data is correct, using techniques like double entry or visual checks.
What is a check digit?
An additional digit appended to a number to verify if the entered data is error-free.
How is a check digit calculated using Modulo-11?
By applying modulus division by 11 to determine the check digit.
What is a checksum?
A verification method used to detect if data has been altered or corrupted during transfer, calculated from the data block being sent.
What is a parity check?
A method for verifying if data was transferred correctly, using even or odd parity.
What is a parity bit?
An extra bit added at the end of a byte to maintain the correct parity according to the sender/receiver’s protocol.
What is a parity block?
A combination of horizontal and vertical parity checks used on a block of data during transfer.
How can you mitigate risks to data integrity?
- Use validation and verification during data entry.
- Protect systems against malware and hacking.
- Implement regular data back-ups to prevent accidental data loss.
What is a parity byte?
A parity byte is an additional byte sent with transmitted data to enable vertical parity checking, alongside horizontal parity checking.
What is Automatic Repeat Request (ARQ)?
ARQ is a type of verification check used to ensure data is received correctly.
What is an acknowledgement in data transmission?
A message sent to the sender to confirm that data has been received without error.
What is validation?
A method of checking if entered data is reasonable and within given criteria, but it does not confirm if the data is accurate or correct.
Can validation detect accurate data entry mistakes?
No, validation checks if data is reasonable, but it cannot verify its accuracy (e.g., entering age as 62 instead of 26 would pass validation).
What are common types of validation tests?
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- Type check: Ensures data is of the correct type (e.g., numbers only in numeric fields).
- Range check: Ensures data falls within specified limits.
- Format check: Ensures data matches a required format (e.g., date format).
- Length check: Ensures data has the required number of characters.
- Presence check: Ensures mandatory fields are not left empty.
- Existence check: Ensures referenced data or files actually exist.
- Limit check: Checks either the upper or lower limit (but not both).
- Consistency check: Ensures related fields have logically consistent data.
- Uniqueness check: Ensures entered data is unique (e.g., usernames).
Give an example of a type check validation.
Entering “sk.34” in a price field would fail, but entering “34.50” would pass.
What is a range check, and give an example.
It checks if data falls within set limits. Example: Entering age as “-120” fails; “48” passes.
Provide an example of a format check validation.
Entering a date as “12-12-20” fails if the format is “dd/mm/yyyy”, while “12/12/2020” passes.
What is a length check with an example?
It verifies if data meets required length. Example: A phone number “012 345 678” fails if 11 digits are needed, while “012 345 678 90” passes.
What is a presence check with an example?
Ensures required fields are filled. Example: Leaving a passport number field empty fails, while “AB 1234567 CD” passes.
What is an existence check with an example?
Verifies if data or a file exists. Example: Searching for non-existent car registration “A123BCD” fails, while finding “books_in_stock” in a database passes.
What is a limit check with an example?
Checks data against a single limit. Example: Entering “-25” for age fails if negative values are not allowed; “72” passes if the upper limit is 140.
What is a consistency check with an example?
Ensures data in related fields is logically consistent. Example: Selecting “Mr” as a title and “female” as gender fails; selecting “Ms” and “female” passes.
What is a uniqueness check with an example?
Ensures data is unique. Example: Choosing “MAXIMUS222” fails if already taken; website name “Aristooo.com” passes if it’s unused.
What is verification in data entry?
Verification is a method of preventing errors when data is manually entered or transferred between computers.
What are the three common methods of verification during data entry?
- Double Entry: Data is entered twice by two people and compared for discrepancies.
- Visual Check: Data on the screen is compared with the original document to identify errors.
- Check Digits: An additional digit is added to a number to detect errors during data entry.
How does double entry verification work?
Data is entered twice, often by two different individuals, and the entries are compared to identify inconsistencies.
What is a visual check in verification?
A manual comparison of the entered data with the original source document to ensure accuracy.
What is a check digit?
An extra digit added to a number (usually at the end) to help detect errors like incorrect entries, transpositions, omissions, or phonetic mistakes.
Where are check digits commonly used?
In barcodes, ISBNs (books), and VINs (vehicle identification numbers).
What types of errors can check digits detect?
- Incorrect digits: e.g., entering 8190 instead of 8180.
- Transposition errors: e.g., entering 8108 instead of 8180.
- Omitted or added digits: e.g., entering 818 or 81180 instead of 8180.
- Phonetic errors: e.g., entering 13 (thirteen) instead of 30 (thirty).
What is the modulo-11 method for calculating check digits?
- Assign weightings from 7 to 1 (left to right) to each digit in a 7-digit number.
- Multiply each digit by its weighting and sum the results.
- Divide the total by 11 and find the remainder.
- Subtract the remainder from 11 to get the check digit (if the result is 10, ‘X’ is used).
Can you provide an example of modulo-11 check digit calculation?
- Number: 4 1 5 6 7 1 0
- Weightings: 7, 6, 5, 4, 3, 2, 1
- Calculation: (7×4) + (6×1) + (5×5) + (4×6) + (3×7) + (2×1) + (1×0) = 106
- 106 ÷ 11 = 9 remainder 7
- 11 − 7 = 4 (check digit)
- Final number: 4 1 5 6 7 1 0 4
If an incorrect number like 4 1 5 7 6 1 0 4 is entered and it does not pass check digit verification. The recalculated check digit would be 3 instead of 4, indicating an error occurred during data entry.
How does the check digit help detect errors?
When the number is re-entered, the check digit is recalculated. If the new check digit doesn’t match the original, an error is detected.
What is verification during data transfer?
Verification during data transfer ensures data is not corrupted or lost when sent electronically between devices.
What are some common methods of verification during data transfer?
- Checksums
- Parity Checks
- ARQ
What is a checksum?
A checksum is a value calculated from a block of data and sent along with the data to detect any changes or corruption during transmission.
How is a checksum calculated?
- Add all the byte values in the data block.
- If the sum (X) is ≤ 255, the checksum equals this value.
- If X > 255:
- Divide X by 256: X / 256
- Round down the result to get Y.
- Multiply Y by 256 to get Z.
- Subtract Z from X: X - Z (this is the checksum).
Example of checksum calculation:
- Sum of bytes (X) = 1185
- 1185 / 256 = 4.629 → Y = 4 (rounded down)
- 4 times 256 = 1024 (Z)
- 1185 - 1024 = 161 (checksum)
How does a checksum detect errors?
The sender’s checksum is compared with the receiver’s recalculated checksum. If they differ, an error occurred, triggering a request to resend the data.
What is a parity check?
A parity check uses a parity bit to detect errors in data transmission, ensuring the correct number of 1-bits based on even or odd parity.
What is a parity bit?
An extra bit added to a byte before transmission to ensure the total number of 1-bits is even (even parity) or odd (odd parity).
How does even parity work?
The parity bit is set so the total number of 1-bits is even.
- Example: Data = 1 1 0 1 1 0 0 (4 ones → already even)
- Parity bit = 0 → Final byte: 0 1 1 0 1 1 0 0
How does odd parity work?
The parity bit is set so the total number of 1-bits is odd.
- Example: Data = 1 1 0 1 1 0 0 (4 ones → even)
- Parity bit = 1 → Final byte: 1 1 1 0 1 1 0 0
How does a parity check detect errors?
After transmission, the receiver recalculates the parity. If it doesn’t match the agreed parity (even/odd), an error is detected.
Example of parity error detection:
- Sender’s byte (even parity): 0 1 0 1 1 1 0 0 (4 ones → even)
- Receiver’s byte: 0 1 0 0 1 1 0 0 (3 ones → odd)
- Result: Error detected because parity changed from even to odd.
Can a parity check identify the exact bit in error?
No, it can detect that an error occurred but cannot specify which bit is incorrect.
What is the method of parity blocks in error checking for transmitted data?
Parity blocks involve performing a parity check both horizontally and vertically on a block of data to identify and locate errors. The method uses a parity byte that indicates the result of the vertical parity check and marks the end of the data block.
What does a parity byte represent in the parity block method?
The parity byte consists entirely of the parity bits from the vertical parity check of the data block and also indicates the end of the transmitted data block.
When might it be impossible to locate an error using the parity block method?
It may be impossible to locate the error if an even number of bits change value during transmission, as this would not alter the overall parity in a way that helps identify the specific error.
What is Automatic Repeat Request (ARQ) in error checking?
ARQ is a method that involves sending an acknowledgment message to confirm correct data receipt, and requesting a re-send if an error is detected, or if a timeout occurs before acknowledgment.
How does ARQ work when no error is detected in transmitted data?
If no error is detected, a positive acknowledgment is sent to the sender to confirm that the data has been received correctly.
What happens if an error is detected during data transmission using ARQ?
If an error is detected, the receiving device requests the sending device to re-send the data packet.
How does ARQ handle timeouts?
If a timeout occurs (i.e., the acknowledgment is not received within a specified time), the sending device will re-send the data packet.
What is the purpose of ARQ in mobile phone networks?
ARQ is used in mobile phone networks to ensure data integrity by managing errors and ensuring reliable transmission.
