Fujitsu Laboratories, National Institute of Information and
Communications Technology, and Kyushu University jointly broke a world
cryptography record with the successful cryptanalysis of a 278-digit
(923-bit)-long pairing-based cryptography, which is now becoming the next
generation cryptography standard.

Until now, cryptanalysis of pairing-based cryptography of
this length was thought impossible as it was estimated to take several hundred
thousand years to break. Indeed, despite numerous efforts to use and spread
this cryptography at the development stage, it wasn’t until this new way of
approaching the problem was applied that it was proven that pairing-based
cryptography of this length was fragile and could actually be broken in 148.2
days. This result is used as the basis of selecting secure encryption technology,
and is proving useful in the standardization of next-generation cryptography in
electronic government systems in Japan and international
standardization organizations.

Many cryptography systems are used from the viewpoint of information
security on a modern information system. Recently, much attention has been paid
to the new “pairing-based” cryptography system, which is being
standardized as a next-generation encryption system. The technology is
attractive as it can be used for various useful applications such as
“Identity-based encryption”, “keyword searchable
encryption”, and “functional encryption”, which were impossible
using previous public key cryptography.

As cryptanalytic techniques and computers become more
advanced, cryptanalytic speed accelerates, and conversely, cryptographic
security decreases. Therefore, it is important to evaluate how long the
cryptographic technology can be securely used. On the other hand, pairing-based
cryptography has not advanced, so it was premature to evaluate its security
against a new attack method.

As for a security evaluation of cryptographies, we succeeded
with the cryptanalysis of the pairing-based cryptography of 278 digits (923
bits) by using 21 personal computers (252 cores) in 148.2 days. The
cryptanalysis is the equivalent to spoofing the authority of the information
system administrator. As a result, for the first time in the world we proved
that the cryptography of the parameter was vulnerable and could be broken in a
realistic amount of time.

This was an extremely challenging problem as it required
several hundred times computational power compared with the previous world
record of 204 digits (676 bits). We were able to overcome this problem by
making good use of various new technologies, that is, a technique optimizing
parameter setting that uses computer algebra, a two dimensional search
algorithm extended from the linear search, and by using our efficient programming
techniques to calculate a solution of an equation from a huge number of data,
as well as the parallel programming technology that maximizes computer power.

This result is not just a new world record of cryptanalysis,
it also means the acquisition of valuable data that forms a technical
foundation on which to estimate selection of secure encryption technology or
the appropriate timing to exchange a key length. We will continue to move
forward on research that pushes the boundary of the secure use of cryptography.

Source: Fujitsu Laboratories