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Java Programming [Archive] - Data Structure
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Posts:37,103
Registered: 3/30/99
Re: Data Structure  
Jul 28, 2004 12:20 PM (reply 15 of 17)



 
Two of my favorite bf number examples:

The classic tale--I don't recall the details--where the king promised to pay somebody an amount of grain equivalent to placing one grain on the first square of a chessboard, twice as much on the next square, etc.--2^64 - 1 grains of wheat or whatever. That's a lot.

The other one was in a book on crypto. To put an upper bound on the number of bits needed to make an average brute force attack take 100 years or something like that. Assume our memory is a blob of silicon the size of the moon, with one bit taking on Si atom. Assume a temperature of 1 Kelvin or something. Assume such and such energy available, number of operations per second, etc. Create a ridiculously powerful physical model, figure out how many keys it could try in a hundred years, and then since there's no chance of getting anywhere near that much power in mankind's forseeable future, use enough bits to produce twice that many keys, and that's how many bits you need to expect an average of 100 yrs. protection against a brute force attack.
 

Posts:5,965
Registered: 5/17/03
Re: Data Structure  
Jul 28, 2004 12:33 PM (reply 16 of 17)



 
To be continued,

http://forum.java.sun.com/thread.jsp?forum=426&thread=542114&tstart=0&trange=15
 

Posts:10,972
Registered: 10/23/03
Re: Data Structure  
Jul 29, 2004 4:36 AM (reply 17 of 17)



 
To be continued,

http://forum.java.sun.com/thread.jsp?forum=426&thread=5
2114&tstart=0&trange=15

That's his largest combination yet: C(500,50) = 2,314,422,827,984,300,469,017,756,871,661,048,812,545,657,819,062,792,522,329,327,913,362,690

The funniest thing would be, after it sinks in that one can't generate collections (or anything) that big,
he'll leaves grumbing, "Java is cräp, I knew I should have coded in C..."
 
This topic has 17 replies on 2 pages.    « Previous | 1 | 2 |