At 04:30 PM 10/10/95 -0700, benny@SIRIUS.COM (Thomas Gorman) wrote:
I'm a bit new to the Crypto Field but I know enough. I heard that the Cypherpunks ran a brute force attack on Netscape's 40-Bit code but I still don't know how those two guys in Berkeley broke the 40-bit in just a few minutes. Can someone on this list explain it to me? Thanks.
Netscape uses a random session key, which feeds that 40-bit encryption. How does it get a random session key without bothering the user to type in random numbers? By using the sources of randomness available to it, like the system clock and process id. Well, since you know when a message was sent, you know what time it was (to the second), and there aren't very many possible values of microseconds available. There also aren't a lot of possible processids, especially when you can run a process on the machine or convince sendmail into telling you. So instead of having 2^40 numbers to brute-force, there were fewer than 2^30, often more like 2^20. That's pretty fast. The third crack was to notice that Netscape isn't very careful with array bounds (in true C fashion), allowing you to push stuff on the stack by handing it a URL with a very long name. If you're careful, you can put interesting stuff on the stack, so it does more than just crash in an ugly fashion. However, three's a charm, and it's now time to Hack Microsoft, especially since Microsoft has been saying bad things about Netscape, when almost every encryption product in a Microsoft tool is wimpy beyond repair, and when their newest and niftiest stuff also has 40-bit keys for export versions, with out even as much salt as Netscape used. #--- # Thanks; Bill # Bill Stewart, Freelance Information Architect, stewarts@ix.netcom.com # Phone +1-510-247-0664 Pager/Voicemail 1-408-787-1281 #---