0x0 Cryptanalysis

vendredi 21 juillet 2017, 20:54  #1
Cryptanalysis : RSA - padding
berceanbogdan
  • 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
nonstandardmodel
  • 8 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 :

s.sendall("{}\n".format(encrypted_msg))

...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.

s.sendall("{}".format(encrypted_msg))

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