[Owasp-leaders] Is it ok to share the PGP Keys and keep thePassPhrase private?

James McGovern JMcGovern at virtusa.com
Thu Oct 14 14:26:33 EDT 2010


If you are married to the scheme of sharing keys but not necessarily the approach (e.g. PGP), then maybe there is an opportunity for you to noodle usage of the Identity Based Encryption work out of Stanford (with patterns from Voltage). The idea is that a key doesn't have to be something based on complex algorithms such as factoring of large prime numbers but could be something as simple as using an email address.  Google for 'identity based encryption' for more information.

 

James McGovern
Insurance SBU 

Virtusa Corporation

100 Northfield Drive, Suite 305 | Windsor, CT | 06095

Phone:  860 688 9900 Ext:  1037 | Facsimile:  860 688 2890  

  <http://www.virtusa.com/>    <http://www.virtusa.com/blog/>    <https://twitter.com/VirtusaCorp>    <http://www.linkedin.com/companies/virtusa>    <http://www.facebook.com/VirtusaCorp> 

 

From: owasp-leaders-bounces at lists.owasp.org [mailto:owasp-leaders-bounces at lists.owasp.org] On Behalf Of Carlos Serrão
Sent: Thursday, October 14, 2010 11:35 AM
To: owasp-leaders at lists.owasp.org
Subject: Re: [Owasp-leaders] Is it ok to share the PGP Keys and keep thePassPhrase private?

 

Dinis,

 

I'm not a crypto expert, but on any public-key based crypto system, the private key is supposed to be always private - even if the private key is protected by a passphrase.

 

It's like using a strong security measure and then use a weaker one to protect the system. It doesn't make any sense.

 

You have clever ways to subvert the passphrase without using a brute force attack:

- dictionary attacks

- social engineering

- shoulder surfing

- others.

 

So, in my opinion this is a bad idea.

 

Best regards.

 

On 2010/10/14, at 10:38, dinis cruz wrote:





Here is a question to the Crypto experts (which I'm not).

From a security point of view, is it ok if I publish both Public and Private PGP Keys but keep the PassPhrase secret?

My assumption is that: "as long as the PassPhrase is strong enough, it would be not practical to brute force it (even if the attacker knows the Private Key)". In fact, should the question be: "How big does the PassPhrase be in 2010/2011 time frame for it to be secure?"

 To see this in practice check out the latest script/tool that I just added to the OWASP O2 Platform <http://o2platform.com/wiki/Download>  which dramatically simplifies the process of using PGP (creating keys, encrypting/decrypting text and encrypting/decrypting files):

*	blog post: http://diniscruz.blogspot.com/2010/10/tool-using-openpgp-to-encrypt-or.html 
*	Wiki page http://www.o2platform.com/wiki/O2_Script/Tool_-_Using_OpenPgp_to_Encrypt_or_Decrypt.h2 
*	YouTube Video http://www.youtube.com/watch?v=_Cd8AfZyWMs 

As you can see, this O2 tool will really enable this workflow (sending the both Public and Private Keys to the client in a non-encrypted zip and then sending the PassPhrase in an offline/out-of-band method), so I'm really trying to figure out if this is a good idea :)

Finally, for the really hard-core crypto guys, can you take a look at how I implemented the BouncyCastle Crypto APIs to make sure I did it correctly: http://code.google.com/p/o2platform/source/browse/trunk/O2_Scripts/APIs/OpenPgp/API_OpenPgp.cs

Thanks 

Dinis Cruz

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--

Carlos Serrão

ISCTE-IUL/ISTA/DCTI | ADETTI-IUL/NetMuST | PT.OWASP

 


Virtusa was recently ranked and featured in 2010 Global Services 100, IAOP's 2010 Global Outsourcing 100 sub-list, 2009 Deloitte Technology Fast 500 and 2009 Dataquest-IDC Best Employers Survey among others.

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