Decryption can be parallelize

[mpgn]

As we can read in the document of the CBC cipher mode : https://en.wikipedia.org/wiki/Block_cipher_mode_of_operation#Cipher_Block_Chaining_(CBC)

decryption can be parallelized

So we can had a level of parallelization to decrypt more quickly the encrypted text.

For each request send to the server, we can try to decipher one byte for each block we have. This way the randomness decreases regarding the number of block.

Check the screenshot bellow:

Without parallelization: ~6.5s

Chance to get one byte: 1/256

With parallelization: ~2.5s

Chance to get one byte: number_of_block/256 if the last byte of every request send to the oracle are different, then number_of_block-1/256, number_of_block-2/256 etc
Worst case: 1/256, best case number_of_block/256.

With this improvement we can decipher so much faster the encrypted text.

[mpgn]

For now, this is only working on the poc but not in the exploit. I didn't find a proper way to duplicate the data send by the client on the proxy and have a proper response from the server.