security estimates

The cryptopocalipse is near(er)!

That’s at least what NIST, CNSS and NSA think.

The primary reason for deploying cryptographic systems is to protect secrets. When the system carries information with a very long life (like locations of nuclear silos or evidence for marital infidelity) you need to stop using it well before it is broken. That means the usable life of a crypto-system is shorter than the time it remains unbroken.

Suite B is a set of cryptographic algorithms in very specific configurations that was originally published in 2005. Implementations certified by NIST in the FIPS program were allowed for protection of SECRET and TOP SECRET information depending on specific key sizes used. In practice SECRET was equivalent to 128 bit level of security, so SHA-256 signatures, AES-128 and P-256 curve, TOP SECRET required 192 bit level of security with SHA-384 signatures, P-384 curve and AES-256 for encryption.

They now claim that quantum computers are much closer than we think (less than 10 years time frame) and as such the keys used for protection of secure information need to be increased in short term (significantly in case of ECC) and research of quantum resistant algorithms is now a priority.

New recommendations

That means we get a new set of recommendations.

To summarise:

If you’re using TLS or IPsec with Pre-Shared Keys (PSK) with AES-256 encryption, you’ll most likely be fine.

If you were planning deployment of ECC in near future, you should just increase key sizes of existing RSA and DH systems and prepare for deployment of quantum resistant crypto in near future instead.

For RSA and finite-field DH (a new addition to Suite B but very old crypto systems by their own right) the recommended minimum is 3072 bit parameters. That is not particularly surprising, as that is the ENISA as well as NIST recommendation for 128 bit level of security.

What is a bit surprising is that they have changed the minimum hash size from 256 to 384 bit.

For ECC systems the P-256 curve was degraded to be secure enough only to protect unclassified information, so it was put together with 2048 bit RSA or DH. The minimum now is P-384 curve.

So now the table with equivalent systems looks like this:

 LoS RSA key size DH key size ECC key size Hash AES key size
112 bit 2048 bit 2048 bit 256 bit SHA-256 128 bit
128 bit 3072 bit 3072 bit 384 bit SHA-384 256 bit

What does that mean?

Most commercial systems don’t need to perform key rotation and reconfiguration of their systems just yet, as the vast majority of them (nearly 90%) still use just 2048 bit RSA for authentication. What that does mean is that the recent migration to ECC (like ECDHE key exchange and ECDSA certificates) didn’t bring increase in security, just in speed of key exchange. So if you’re an admin, that means you don’t need to do much, at least not until other groups of people don’t do their part.

Software vendors need to make their software actually negotiate the curve used for ECDHE key exchange. Situation in which 86% of servers that can do ECDHE can do it only with P-256 is… unhealthy. The strongest mutually supported algorithms should be negotiated automatically and by default. That means stronger signatures on ECDHE and DHE key exchanges, bigger curves selected for ECDHE and bigger parameters selected for DHE (at least as soon as draft-ietf-tls-negotiated-ff-dhe-10 becomes a standard).

Finally, we need quantum computing resistant cryptography. It would be also quite nice if we didn’t have to wait 15 or even 10 years before it reaches 74% of web servers market because of patent litigation fears.