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Crypto battle gets ugly

October 12, 1998
Web posted at: 1:15 PM EDT

by Ellen Messmer


(IDG) -- REDWOOD SHORES, California -- Under the probing eyes of security experts, encryption products undergo the kind of intense peer-review scrutiny seldom seen anywhere else in the information-technology industry.

But sometimes vendors refuse to reveal as much as security experts would like. Then tensions flare into bitter argument, such as the ugly battle breaking out this week between TriStrata Security here and Minneapolis-based cryptography expert Bruce Schneier.

Schneier, who has made headlines as the security guru who exposed security flaws in everything from cell phones to Microsoft encryption software, is now accusing TriStrata of presenting false information about its flagship product, the TriStrata Enterprise Security Server (TESS). TriStrata is firing back that Schneier is just out for revenge because TriStrata won't let him do a technical review of the product -- something for which Schneier wants to charge a fee.

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TriStrata's vice president of business development Bill Atalla refused to respond directly to the accusations made in Schneier's scathing critique of TESS published today on the Web. In it, Schneier argues that TESS does not even work with the technology TriStrata says it does -- something called "one-time pad" -- and that TriStrata is basically lying about its security architecture. In fact, Schneier's report claims it's a practical impossibility to achieve the kind of "unbreakable" encryption TriStrata claims to have in its enterprise server that manages an entire organization's security policy.

"It's his speculation based on what little he has seen," counters Atalla about the devastating report, adding TriStrata only allows prospective customers, mostly the Fortune 500, to get a close look (under non-disclosure) at the high-ticket TESS, which can cost in the million-dollar range.

"Our technology is revolutionary, we have patents pending," explained Atalla. "We reveal details on a need-to-know basis with these companies."

TriStrata did have University of London crypto expert Dr. Fred Piper review TESS in a positive light, but the company is not making that report available yet.

Schneier says TESS, a central server that requires the user to log on to get permission to encrypt and decrypt files, is impractical to use in the real world anyway because if the user can't get to a network to reach the server, he can't even decrypt his own stored files. He said it's also unclear how two different TESS servers would manage secure information exchange between users registered to two diffeent systems for electronic commerce.

TriStrata acknowledged that remote-access does present a limitation, and that the company is working on a second version of TESS for better remote management. But officials declined to address any other specifics raised in Schneier's report.

According to Schneier, if TESS did use a "one-time pad," an older technology used to secure the U.S.-Soviet hotline TTY devices in the Cold War days, it might indeed be theoretically unbreakable. But he claims it's impossible to make this work in a modern computer environment because you'd had to create a unique one-time encryption key 1 MB long for a 1M-byte file and get that key securely to the file's recipient each time.

Schneier, basing his judgement on some of TriStrata's documentation -- and that mysterious crypto grapevine where all secrets are ultimately shared -- believes TESS actually uses a "pseudo one-time pad," also known as a one-time stream cipher.

According to Schneier, that means TESS relies on an private encryption algorithm that TriStrata is refusing to acknowledge or publish for review for crypto experts who will scrutinize its mathematical strength to determine if it's breakable or not.

It's very hard to create an algorithm that no one else can break, said Schneier in his report. "And the only way to prove that is to subject the algorithm to years of analysis by the best cryptographers around."

He added the commercial world typically relies on the public review process to evaluate the security of systems, and protocols like SSL, IPSec and PKIX undergo this scrutiny as public standards.

About TriStrata's TESS, Schenier says, "TriStrata has chosen to ignore all public standards in favor of their own proprietary technology, while at the same time refusing to make technical details of the technology public. In order to use their system, the purchaser must trust their cryptographers are better than the collective wisdom of the world's academic cryptographers, that their protocol designers are better than everyone who has worked on the open Internet protocols over the last few years, that their implementors are better than everyone who has made and evalauated the public implementations of those protocols."

For its own part, TriStrata has decided to not respond to Schenier's attack. Atalla would only say, "He's good at P.R., and this is the newest thing on the block, and he's hoping to be part of this paradigm shift. But, we don't want to start a war here."

Schneier does admit he's got clients calling who want to know what TriStrata is about after reading about it in places like the Wall Street Journal, and he does want to get paid to review TESS. But in his final salvo, he adds, "In my back pocket I have a way to break the system, but I can't publish it until I know I'm right."

How the TriStrata Enterprise Security Server works

Every decryption or encryption operation requires a "permit" from the TESS.

The user contacts the TESS over the network so both sides can authenticate each other using a proprietary protocol called the Private Access Line.

TESS seals a permit to the user machine, which is used to encrypt the file or message. TESS also sends a "seal" to the user, which is only readable by the TESS. The user stores the seal with the file (if it is with the file (if it is encrypted locally)) or sends the seal, along with the encrypted message, if transmitted to another user.

To decrypt a file, the user retrieves the seal and sends the seal to the TESS along with authentication data from the PAL protocol. TESS opens the seal, and determines whether the user is allowed to decrypt this data. If so, the TESS sends a decryption permit to the user so the local machine can use it to decrypt the file or message.

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