Fermi estimates

Johan Wevers johanw at vulcan.xs4all.nl
Fri Nov 14 16:48:14 CET 2014

On 14-11-2014 16:01, Philip Jackson wrote:

> Does anything prevent the key breaker getting lucky and cracking it first try?

No. It's just extremely unlikely.

> It seems to me that all discussions on key breaking with their very large
> numbers always assume that the last try is THE ONE.

Nu, usually one assumes that brute forcing requires, on average,
scanning half the keyspace.

> And how does the cracker know he has succeeded ?

That's the tricky part. If the output of the encryption program is just
encrypted text, the only way is to see if there's something recognizable
in the decrypted stuff. But most software includes some kind of CRC
check or a hash so that can be checked. GnuPG does this.

> Does he have to pause between
> each iteration to see if he has 'something good' ?


ir. J.C.A. Wevers
PGP/GPG public keys at http://www.xs4all.nl/~johanw/pgpkeys.html

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