0x0 Cryptanalysis

vendredi 21 juillet 2017, 20:54  #1
Cryptanalysis : RSA - padding
  • 1 posts

The oracle tells me the flag ciphertext is not padded correctly. Is this intended or am I doing something wrong ? Thanks !

vendredi 12 octobre 2018, 21:32  #2
Cryptanalysis : RSA - padding
  • 10 posts

I have lost like almost an hour to pass this problem. So for anybody in the future loosing his/her mind over this, here is what was my problem...
I was using python script to send the encrypted-text to Oracle. Something like :


...and if I send the flag text (that should be decrypting correctly) I got "[-] PKCS#1_5 : error" message. After some desperate attempts to get it working I tried to send it without the ’\n’ (new line char) at the end and it worked.


Seems that the Oracle is checking if the length is 256 bytes and takes the message without the need for ’\n’.