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Re: stealing ssh keys
From: "Thor (Hammer of God)" <thor () hammerofgod com>
Date: Fri, 26 Oct 2012 12:58:37 -0700

Actually, the DSA key is used to sign the message in many applications, though I've often wondered exactly what 
reduction in security exists if the paired private key is used to sign material instead. Do you have any info on that?  
I've asked industry leaders in crypto, and while they report it should be avoided, I've never received any quantified 
answer.

And just to make sure people understand (like the guy you replied to), the *message* is not encrypted with the pubic 
key - the *key the message is encrypted with* is encrypted with the public key.   While you CAN asymmetrically encrypt 
some data (116 bytes with a 1024 RSA key), it is the symmetric key (e.g. AES) which gets encrypted/decrypted with PKI 
keys and th AES key used to encrypt and decrypt the message itself. 

I'm sure you knew ht, but others obviously don't. :). 

Sent from whatever device will keep us from debating which one is better.

On Oct 24, 2012, at 11:51 PM, Ivaylo Hubanov <sniffski () gmail com> wrote:

Yes Raj,
You almost got the RSA encryption/decryption flow. :) Just the private key is used to sign the data and not to 
encrypt it. 
Check this "http://en.wikipedia.org/wiki/Public-key_cryptography";
Each user has a pair of cryptographic keys - a public encryption key and a private decryption key.
...
The two main uses for public-key cryptography are:
- Public-key encryption: a message encrypted with a recipient's public key cannot be decrypted by anyone except a 
possessor of the matching private key - it is presumed that this will be the owner of that key and the person 
associated with the public key used. This is used to attempt to ensure confidentiality.
- Digital signatures: a message signed with a sender's private key can be verified by anyone who has access to the 
sender's public key, thereby proving that the sender had access to the private key and, therefore, is likely to be 
the person associated with the public key used. This also ensures that the message has not been tampered with (on the 
question of authenticity, see also message digest).

regards,
sniffski
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