Timeline for CBC KEY recovery when KEY=IV
Current License: CC BY-SA 4.0
15 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Dec 4, 2023 at 14:49 | comment | added | poncho | @Sahar: oops, I see you're correct - the decryptor only returns a boolean. In that case, the padding attack is the best you can do... | |
| Dec 4, 2023 at 14:30 | comment | added | Sahar | but the decrypt function does not return the plaintext, it only returns True/Flase so i guess the only solution to find the key is by performing padding oracle attack. | |
| Dec 4, 2023 at 13:53 | comment | added | poncho | @Sahar: using the value $E_k(k)$, you craft a ciphertext so that the decryption tells you the value $k$. Note that the padding has to be correct (so you get the decrypted plaintext and not a decryption failure). To do that, consider the processing during CBC mode decryption... | |
| Dec 4, 2023 at 8:29 | comment | added | Sahar | Thanks for your help i really appreciate it. One last question, what is the more efficient way? | |
| Dec 4, 2023 at 5:24 | vote | accept | Sahar | ||
| Dec 3, 2023 at 21:32 | comment | added | poncho | @Sahar: well, yes, I suppose you could use a padding oracle attack - however, there is a far more efficient way (things get a lot easier for the attacker when there is no MAC). | |
| Dec 3, 2023 at 16:25 | comment | added | Sahar | omg so after we get C1 in the above step (which in this case we can say that IV is the message and P1 which is all zero is the IV since x XOR y is same as y XOR x) then we can do padding oracle attack to reconstruct IV which is the key. Am i right? | |
| Dec 3, 2023 at 16:17 | comment | added | Sahar | if P1 is all zero then we get enc(KEY, KEY) | |
| Dec 2, 2023 at 19:02 | comment | added | poncho | @Sahar: Ok, then, how do we select a plaintext (P1) so that we can learn the value $enc(KEY, KEY)$? | |
| Dec 2, 2023 at 16:36 | comment | added | Sahar | C1 = enc(KEY, P1 XOR KEY) | |
| Dec 2, 2023 at 14:02 | comment | added | poncho | @Sahar: ok, then, during encryption, how is the first ciphertext block generated? | |
| Dec 2, 2023 at 11:04 | comment | added | Sahar | of course yes i know. | |
| Dec 1, 2023 at 13:17 | comment | added | poncho | @Sahar: do you know what processing is done during CBC mode encryption? In CBC mode decryption? | |
| Dec 1, 2023 at 12:35 | comment | added | Sahar | I couldnt figure out what you mean. Can you explain? | |
| Nov 29, 2023 at 20:00 | history | answered | poncho | CC BY-SA 4.0 |