Whit Diffie on Encryption and PKI

Crypto pioneer Diffie on the developments in encryption and the relevance of PKI. (Part of the What Happens Next security predictions series.)

In the 1970s, Whitfield Diffie co-wrote the recipe for one of today's most widely used security algorithms in a paper called "New Directions in Cryptography." The paper was a blueprint of what came to be known the Diffie-Hellman key exchange, a seismic advancement in Public Key Infrastructure (PKI) technology that makes secure online transactions possible. It's part of such popular protocols as the Secure Sockets Layer (SSL) and Secure Shell (SSH).

But much has happened in the world of security since then, which begs the question: Does the old recipe hold up in today's environment? Diffie answered that and other questions in a recent e-mail exchange:

CSO: The tech landscape has changed considerably since the advent of PKI. Does it still hold up in today's environment? If so, explain where it continues to do good.

Cryptographic algorithms are far and away the best cooked and most successful part of information security. If breaking into Web sites, stealing identities or subverting critical infrastructure required breaking AES or elliptic-curve cryptosystems, we would not be complaining about cybersecurity. Public key cryptography still seems to be the best known solution for moving credentials in unprotected environments. Why is public infrastructure not more successful? One answer is that it is very successful. SSL appears to be the most widely deployed cryptography-based security mechanism of all time.

If SSL is so great why is e-mail, laptop and data storage all so insecure?

Clearly more broadly applicable mechanisms are needed. Why are they not more successful? One possibility is that it is a capital and marketing development problem. Keying infrastructure is like any communications phenomenon: the more people who have telephones, the more valuable each individual phone becomes. As long as only a small amount of peer-to-peer PKI is installed, there is little motivation for any individual user to install it. This problem is aggravated by another: Competing providers and standards fragment the market and dilute interoperability. More important, however, is the problem of implementation.

How so?

IPSec and e-mail encrypters are implemented within existing insecure computer systems. This burdens the PKI with cumbersome lists of compromised keys. Such success as we have had with PKI-based security is often under attack from network providers. Most VPN users have had the experience of trying to communicate security with their corporate networks, only to find that the conference center, university, or even hotel at which they are located blocks the IPSec port.

In the bigger picture, can you point to a technological development in the last five years that will dramatically alter the shape of cryptography going forward -- in other words, a development that is forcing a change in how we've approached cryptography in recent decades?

For the long run, the 2005 announcement of cryptographic Suite B, a set of public algorithms (mostly federal standards) certified for protection of all levels of classified information. If Suite B has as much impact on worldwide cryptographic practice as DES did, we can expect a big improvement in the security and interoperability of cryptographic security systems worldwide.

How does Sun's current strategy fit in with the future direction of cryptography?

OpenSolaris supports a cryptographic framework that provides uniform cryptographic services to both kernel and user processes. The multi-threaded Niagara processor devotes one of the eight cores on each chip to cryptographic services, implementing conventional and public-key cryptography, and supporting all the Suite B algorithms. The SPARC instruction set has been augmented with instructions that support the older (modular-arithmetic-based) public-key cryptography, elliptic curve cryptography, and symmetric cryptography.

One great gap in cryptographic protection is stored data. To address this market, Sun's StorageTek division produces fully encrypted tape drives. This allows tapes to be shipped and stored with untrusted service providers without concern for the security of the data the tapes concern.

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