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Does there exist any software which allows you to extend the keylength for RSA past that limit? It seems arbitrarily short, is this a limit of the number of primes or is there some justification for limits on size other than long computational time?

I've been using gaim-encrypt and GPG for years and it's never made sense why there are restrictions in keysizes.

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Key sizes over 4096 are not currently supported in GPG. The reason for this is that 8192 keys are very slow. If you require a key greater than 4096-bit then you should really thing about what you are using that key for? Are you prepared to have everything encrypted at a ridiculously slow manner for little extra security? Encryption is not a panacea, it is well established that governments try avoid breaking encryption if possible by going after the source e.g. your key passphrase!

It is recommended to use key 2048-bit keys (minimum) currently and these should be ok for the next few years. It is accepted that 1024-bit keys are crackable with current technology. 2048-bit keys should be sufficient until about 2030 and 3072-bit keys from then on.

That being said you can always change the GPG source code to allow keys greater than 4096. There is no technical reason why you cannot use a 8192-bit key. Just change the upper key size limit in keygen.c

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is this a limit of the number of primes |

In fact public key cryptography uses pseudo primes as real random prime numbers are very difficult to generate so we use numbers which are so large it is not feasible to deduce all the factors.

Many people have spent time studying chaotic systems such waves breaking on a beach to help generate real random numbers.

Hope that helps.

Fire Ant

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