The security of modern cryptography is based on number-theoretic computations so hard that the problems are practically impossible for attackers to solve. In practice this means that approaches and algorithms to crack the cryptographic algorithms are known but with the current best technologies it would take too many years to complete an attack.

But what if a shortcut is found at least in some particular cases?

This is exactly what some researches [article, arstechnica] have just found for the Diffie-Hellman (DH) algorithm with 1024bit keys, algorithm which is one of the pillars of the security of Web transactions among many other uses. The researchers have shown that for DH with 1024bit keys there exist some parameters (prime modulus) that allow with current technologies to compute the secret encryption keys in short time. In other words, some parameters adopted in DH-1024 can contain **invisible trapdoors**. The only ways to securely use DH today seem to be:

- to know how the parameters have been generated and to be sure that they do not allow for any “trapdoor”
- or to use DH with 2048bit or larger keys.

What does this teach us about the security that cryptography provides to everyday IT?

How should we implement and manage cryptography within IT security?

Is cryptography joining the “zero days => vulnerabilities => patch management” life-cycle which has become one of the landmarks of current IT security?