3 research outputs found
Removable Weak Keys for Discrete Logarithm Based Cryptography
We describe a novel type of weak cryptographic private key that can exist in
any discrete logarithm based public-key cryptosystem set in a group of prime
order where has small divisors. Unlike the weak private keys based on
\textit{numerical size} (such as smaller private keys, or private keys lying in
an interval) that will \textit{always} exist in any DLP cryptosystems, our type
of weak private keys occurs purely due to parameter choice of , and hence,
can be removed with appropriate value of . Using the theory of implicit
group representations, we present algorithms that can determine whether a key
is weak, and if so, recover the private key from the corresponding public key.
We analyze several elliptic curves proposed in the literature and in various
standards, giving counts of the number of keys that can be broken with
relatively small amounts of computation. Our results show that many of these
curves, including some from standards, have a considerable number of such weak
private keys. We also use our methods to show that none of the 14 outstanding
Certicom Challenge problem instances are weak in our sense, up to a certain
weakness bound
Solving DLP with Auxiliary Input over an Elliptic Curve Used in TinyTate Library
Part 4: AlgorithmsInternational audienceThe discrete logarithm problem with auxiliary input (DLPwAI) is a problem to find α from G, αG, αd G in an additive cyclic group generated by G of prime order r and a positive integer d dividing r − 1. The infeasibility of DLPwAI assures the security of some cryptographic schemes. In 2006, Cheon proposed a novel algorithm for solving DLPwAI. This paper shows our experimental results of Cheon’s algorithm by implementing it with some speeding-up techniques. In fact, we succeeded to solve DLPwAI in a group with 128-bit order in 45 hours with a single PC on an elliptic curve defined over a prime finite field with 256-bit elements which is used in the TinyTate library