Is SSL safe?

[InfoSec News <isn () c4i org>]

http://www.theregister.co.uk/content/55/29868.html

By John Leyden
Posted: 21/03/2003

Czech security researchers this week claimed to have uncovered
weaknesses in SSL that might permit crackers to decypher transmissions
over supposedly secure links.

However, independent cryptography experts, who are studying a paper
from Czech security outfit ICZ, are yet to verify the risk is real and
as serious as ICZ suggests - so the research needs to be treated with
caution.

A press release issued on behalf of Czech cryptologists Vlastimil
Klíma and Tomá? Rosa, both of ICZ, and Ondrej Pokorný, paints a
picture of severe problems with the SSL protocol. It states:

"The weakness identified by the cryptologists makes it possible to
attack the SSL/TLS (Secure Sockets Layer and Transport Layer Security)  
protocols used as a cryptographic protection of a majority of
electronic transactions, such as on-line purchases and e-banking, and,
in some cases, a secured transmission of e-mails as well.

"An attack on these protocols, as described by the team of Czech
cryptologists, can break through the protection completely and decrypt
protected communication. This means for clients using applications
relying on SSL/TLS protocols that an attacker is able to retrieve
their credit card numbers, sensitive information about their bank
accounts and misuse confidential data from their e-mails."

Lordy.

> From the press release and an abstract of their paper we learn that
the researchers have uncovered a possible means of obtaining
cryptographic keys from a server and thereby unlocking the contents of
a captured session. This side-channel attack, which builds on previous
research, is explained in detail in the trio's paper, which you can
read here [1] (PDF).

The Czechs found "two thirds of randomly chosen Internet SSL/TLS
servers were vulnerable" to the attack they document. Improvements to
SSL are put forward in the paper, which, drawing as it does on complex
mathematical analysis, doesn't lend itself to distillation into a news
story.

So how great a risk does the attack present to e-commerce
transactions?

To answer this question we contacted noted cryptographer Bruce
Schneier, CTO of Counterpane Systems. Schneier wasn't available to
provide an immediate response but told us he would be looking into the
issue. We'll let you know what he comes up with.

A month ago Swiss security researchers discovered an attack against
implementations of the ubiquitous SSL protocol that could potentially
compromise email passwords, though not ecommerce transactions.

Writing about this attack in his Cryptogram newsletter, Schneier says
users should be more concerned about their credit cards been lifted
from insecure servers - rather than snapped up in transit, using
either the Swiss or Czech attacks.

"The real risks to personal data are the large databases at the
endpoints, not the communications between them. I wouldn't discard SSL
as being irrelevant, but neither would I worry very much if it could
be attacked. Security is only as strong as the weakest link, and SSL
is nowhere close to being the weakest link," he writes.

[1] http://eprint.iacr.org/2003/052.pdf




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