Theoretical and maybe stupid questions about security

[Robert J. Hansen]

> I wonder how easily my private key(s) ('secgring.gpg') can be cracked
> once somebody get access to it.

No one with two brain cells to rub together will try brute-forcing a  
strong passphrase.  No one.  Assuming your passphrase is strong you  
could publish your secret key in the _New York Times_ and still be  
completely confident in the security of your communications.

> Q: Is the password stored as an hash and can it be cracked using Rainbow
> Tables? Is it maybe salted?

The passphrase isn't stored as a hash, so much as the passphrase is  
hashed (many, many times -- with salt) and the output is used to  
attempt to decrypt the secret key.  The passphrase is never stored,  
though, either in plaintext or in hashed form.