The researchers have demonstrated this exploit works, but does that mean it’s a real world threat for all GnuPG users?
The libgcrypt encryption library as used by the open source Gnu Privacy Guard (GnuPG) has been cracked wide open by researchers from the universities of Adelaide, Eindhoven, Illinois, Maryland and Pennsylvania.
In their paper the researchers display a good sense of humour in calling the vulnerability ‘sliding right into disaster’. That’s because it exploits the fact that exponent bits leaked by the ‘sliding window’ process used by libgcrypt can be used to carry out a key recovery attack against RSA. This despite it previously being thought that even if the entire pattern of squarings and multiplications was observed courtesy of s side-channel attack, it wouldn’t leak enough exponent bits to be of any real use.
However, the researchers managed to demonstrate “a complete break of RSA-1024” as implemented in libgcrypt. They state that this was due to the fact that libgcrypt uses a left-to-right method of computing the sliding window expansion.