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If you don't care about security, you can do that. Otherwise, you absolutely need a different key pair for each user. If multiple users share the same private key, they can easily impersonate each other. If you're only doing key authentication (no passwords) then they can log into each other's accounts.


One of my favourite gems on encryption is from Bruce Schneier in his book Applied Cryptography. One of the consequences of the second law of thermodynamics is that a certain amount of energy is necessary to represent information. To record a single bit by changing the state of a system requires an amount of energy no less than kT, where T is the ...


This sounds like homework to me, but try WolframAlpha; Worst case, you have to try all 2^256 possible values it takes 1836000000000000000000000000000000000000000000000000000000000000 years Best Case, you try one value and it's correct it takes 0.0000005 seconds.


Well, using simple math: If checking one key takes 1000 clock cycles, and the computer has 2,000,000,000 cycles per second, it checks 2 million keys per second. The best case is that the first key you try is correct: total time is half a microsecond. The worst case is that the last key you try is correct: you have 2^256 keys divided by around 2^21 checked a ...


I would not recommend combining random number generators in this way without having some underlying theory to support your case. A simple way to illustrate the issues is to consider the behavior of low-end LCG algorithms, the popular "one-liner" schemes for generating random numbers. These can be made to produce sequences that will pass certain statistical ...


All software vendors know their software can, and always will be cracked. Software has been cracked for as long as there's been licensing or copy protection. Cracking groups go back to the 1980s, and copy protection schemes went as far as punching physical holes in a specific sector in floppy disks. That sector could never be written to on the original ...


If you break into software that I have written then I would much rather be the first to know rather than the last .. Hell if you tell me how you did it and it was creative enough I might even speak with my employers into paying you as a consultant . As long as it was done for non malicious reasons I'm ok with that. But if you break into a system that I run ...

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