Password length paranoia

[Gabriele Alberti]

Hello,
I am not a crypto expert; i have this paranoia since some time though.. 
If i use _symmetric_ cyphers (lets say a 256 bit) how long my password has to
be? 
Keeping in mind my password can be composed with all 95 writeable ascii chars,
using for example a 15 chars password gives me a "password space" of 95^15,
that is  463291230159753366058349609375 passwords..*much* smaller than the 256
bit keyspace (2^256,
115792089237316195423570985008687907853269984665640564039457584007913129639936
keys). With such password, is not easy to bruteforce the password rather than
the actual key? To get a bigger password space, such as it is more convenient
to attack the key against the password, i computed 95^39, that is
135275954279056171880020500846747996912046843238165820366702973842620849609375,
a value just above the 256 bit keyspace..should i really use a 39 chars
password to be safe or i am missing something?

Thanks in advance,

Gabriel



	

	
		
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