I'm reading an article on the Arch Linux wiki about system encryption, in an example the author specified a 512 bit key. From what I read on Wikipedia regarding encryption ciphers it doesn't seem to be secure enough. That leads me to the question: what's the strongest possible key size?
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There isn't any For each key of length |
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RSA itself contains weaknesses, as see RSA Algorithm section "Weaknesses in RSA", as well as Cracking RSA and RSA: Hacking and Cracking. That said, and if the method being used to crack your encryption is only brute force, then the strongest possible key size is the one that will require more computing power than is available to the hacker that is trying to decrypt your messages, or more time than he is willing to spend. Recently, a 200-long RSA key was factored in 50 years of computer time, and 307-long in 100 years of computer time. I suppose even 128-bit will still take a few years of computer time. 1024 bits might be proof against most crime-rings, but so are probably 512-bits and even 128-bit. 1024 bits is surer, but do you expect an agency with the computing-power of the US National Security Agency to be used against you ? If all you are trying to protect yourself against is the neighborhood script-kiddo, then 128 bits are enough. If you are trying to protect your bank transactions, then no hacker wastes his time trying to decrypt RSA, but rather will try to trick you into installing his trojan. |
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The RSA recommends:
so I would go for at least 1024 bits. Note that the bigger the key size, the slower the encryption/decryption will be. |
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I personally use a 2048-bit key, and find that my CPU can keep up with the maximum bandwidth of my SATA drive with no problems. I'd recommend a 2048 on any modern hardware (1GHz or faster processor). |
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