Data integrity
Cyber security Lesson 13 1:29 English narration · English + 中文 subtitles burned in
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Transcript
Integrity means data stays accurate, and two techniques protect it.
完整性的意思是数据保持准确，有两种技术在保护它。
They sound alike and the exam loves separating them, so watch what each one asks.
它们听起来很像，而考试最爱考它们的区别， 所以看清楚每一种究竟在问什么。
Validation asks: is this data reasonable?
验证问的是：这个数据"合理"吗？
A range check, a length check, a format check, a presence check.
范围检查、长度检查、格式检查、非空检查。
Verification asks something completely different: was this data copied correctly?
核对问的完全是另一件事：这个数据"抄对了"吗？
Double entry, or reading it back.
双录入，或者读回来核一遍。
A mistyped age of ninety-nine is perfectly reasonable and still wrong.
一个打错成 99 的年龄完全"合理"，但它依然是错的。
There is a third place data goes wrong: on the way.
数据出错还有第三个地方：路上。
When data travels, bits can flip.
数据在传输时，比特位可能翻转。
A checksum catches that.
校验和能抓住这件事。
The sender calculates a small number from the data itself and sends it along.
发送方从数据本身算出一个小小的数字，跟着一起发过去。
The receiver recalculates the same number from what actually arrived.
接收方拿真正收到的东西，把同一个数字再算一遍。
Here one digit changed, so the two totals disagree — and disagreeing totals mean the data was corrupted.
这里有一位数字变了，于是两个总数对不上—— 而总数对不上，就意味着数据在路上损坏了。
Four things to take with you.
带走四点。
One: validation asks whether the data is reasonable.
第一：验证问的是数据是否合理。
Two: verification asks whether it was copied correctly.
第二：核对问的是数据是否抄对了。
Three: a checksum is computed from the data itself.
第三：校验和是从数据本身算出来的。
Four: recalculate it at the other end and compare.
第四：在另一端把它重算一遍再比对。
Now compute a check digit in the task below.
现在去下面的题里算一个校验位。