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Netsacpe's Offical Response

Originally From [email protected]  Thu Aug 17 11:42:39 1995
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Date: Thu, 17 Aug 1995 08:44:45 -0700
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To: [email protected]
From: [email protected] (Peter Shank)
Subject: Netscape security

Glen,

We're sending this response to the press and interested parties; it may also get posted on home.netscape.com.

Best regards...

-Peter

Late Tuesday evening a person from France posted a news article to the
hacker community claiming success at decrypting a single encrypted message
that had been posted as a challenge on the Internet sometime on or before
July 14, 1994. His response to the challenge is described in an email that
has been forwarded widely across the Internet.

What this person did is decrypt one encrypted message that used RC4-40 for
encryption. He used 120 workstations and two parallel supercomputers for 8
days to do so. As many have documented, a single RC4-40 encrypted message
takes 64 MIPS-years of processing power to break, and this roughly
corresponds to the amount of computing power that was used to decrypt the
message.

Important points to understand:

  1. He broke a single encrypted message. For him to break another message
     (even from the same client to the same server seconds later) would
     require *another* 8 days of 120 workstations and a few parallel
     supercomputers. The work that goes into breaking a single message can't
     be leveraged against other messages encrypted with other encryption
     keys.

  2. The standard way to determine the level of security of any encryption
     scheme is to compare the cost of breaking it versus the value of the
     information that can be gained. In this case he had to use roughly
     $10,000 worth of computing power (ballpark figure for having access to
     120 workstations and a few parallel supecomputers for 8 days) to break
     a single message. Assuming the message is protecting something of less
     value than $10,000, then this information can be protected with only
     RC4-40 security. For information of greater value, currently available
     RC4-128 security should be used.

  3. Inside the US, software can support a range of stronger encryption
     options, including RC4-128, which is 2^88 times harder to break.
     Meaning that the compute power required to decrypt such a message would
     be more than 1,000,000,000,000 (trillion) times greater than that which
     was used to decrypt the RC4-40 message. This means that with forseeable
     computer technology this is practically impossible.

So in conclusion, we think RC4-40 is strong enough to protect consumer-level
credit-card transactions -- since the cost of breaking the message is
sufficiently high to make it not worth the computer time required to do so
-- and that our customers should use higher levels of security, particularly
RC4-128, whenever possible. This level of security has been available in the
U.S. versions of our products since last April. Because of export controls
it has not been available outside the U.S. We would appreciate your support
in lobbying the U.S. government to lift the export controls on encryption.
If you'd like to help us lobby the government send email to
[email protected].

Finally, we'd like to reiterate that all this person has done is decrypt
one single RC4-40 message. RC4 the algorithm and products which use the
algorithm remain as secure as always.