Security Basics mailing list archives
Re[2]: Crypto Question
From: Vishal <dhrakol () myrealbox com>
Date: Mon, 17 Nov 2003 17:14:27 -0500
Hi N407ER Saturday, November 15, 2003, 8:36:58 PM, you wrote: N> If I'm not mistaken, though, the passphrase on the PGP private key is N> simply a bit of symmetric-key encryption to help protect your private N> key in the event that the key itself is compromized. The passphrase is hashed to produce a symmetric key that is then used to encrypt your private key. N> But if you've got your key secured on, say, a CD in a locked drawer, and N> you send an e-mail encrypted with that key, the passphrase (or lack) is N> irrelevent; Not quite. Say someone wanted to impersonate you by digitally signing a message. Or read a confidential message you had been sent. He would need your private key in both these scenarios. And if he managed to break into that drawer, the only thing standing between your private key and him is the passphrase. A strong passphrase can make it orders of magnitude more difficult to access your private key either using brute force or dictionary attacks against the passphrase. Drawer locks aren't usually too difficult to pick. If you had that CD in a locked safe in a locked room guarded by utterly incorruptible guards, you might be justified in picking a weak passphrase. Since it's a drawer, backing up that protection with a strong passphrase is a good idea if maintaining your privacy is important to you. N> an attacker would still have to break the RSA encryption, of N> which the only current known mean is bruteforce. The passphrase really only N> comes into play if your private key is compromized; e.g. the attacker N> breaks into your system and steals your key. Am I incorrect in this N> assumption? Since brute force attacks are impractical for the average attacker, the way he will get around the system is by accessing your private key. This makes the "if your private key is compromised" scenario very much the issue in question, since that is where his efforts will be directed. N> I've never really looked at the internal workings of PGP (but I N> was under the impression its fairly stock RSA). Not always RSA. A number of different symmetric(IDEA, 3DES etc.) and asymmetric (RSA, DH/DSS etc.) ciphers are used. DH/DSS gained popularity due to licensing issues with RSA in recent years. Cheers, -Vishal --------------------------------------------------------------------------- Forum Systems PRESIDIO: PGP / XML GATEWAY APPLIANCE The Presidio integrates PGP data encryption and XML Web Services security to simplify the management and deployment of PGP and reduce overall PGP costs by up to 80%. FREE WHITEPAPER & 30 Day Trial - http://www.securityfocus.com/sponsor/ForumSystems_security-basics_031027 ----------------------------------------------------------------------------
Current thread:
- Re: Crypto Question, (continued)
- Re: Crypto Question Wu Fei Liang (Nov 07)
- Re: Crypto Question Adam Newhard (Nov 07)
- Re: Crypto Question Tomas Wolf (Nov 10)
- Re: Crypto Question Philip Duldig (Nov 11)
- Re: Crypto Question Mitchell Rowton (Nov 17)
- Re: Crypto Question Florian Streck (Nov 17)
- RE: Crypto Question Hagen, Eric (Nov 07)
- RE: Crypto Question Hagen, Eric (Nov 07)
- Re: Crypto Question N407ER (Nov 17)
- RE: Crypto Question Kenneth Buchanan (Nov 07)
- Re[2]: Crypto Question Vishal (Nov 17)
- Re: Crypto Question Chris Berry (Nov 17)