Hello,
I have some questions. I the previous lecture we said that Authenticity and data integrity are closely related.
1) But can we clearly say the following : Authenticity is respected <=> data integrity is respected.
Here is my reasoning :
- Authenticity is respected => The msg comes from Alice so it's not modified.
- Data integrity is respected => the received msg = the original message = Alice's message.
2) If the message is modified by error (bits swiped or lost). Can we consider that data integrity is not respected ? What about authenticity (because Bob can't be sure that the sender is actually Alice, due to the error) ?
3) If Persa intercepts Alice's message but doesn't change it, then sends it to Bob. Is the authenticity still respected ? (because Persa's msg = Alice's msg). Notice that if your answer is "no", it means that data integrity is respected but authenticity is not, which contradicts my reasoning in step b).