full-disclosure - Re: stealing ssh keys

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Message-ID: <CAH8yC8mh0ibtK1YgZZ2OO2RPa36hFGo5DcSzjFQn39ow-BewVA@mail.gmail.com>
Date: Mon, 29 Oct 2012 07:49:54 -0400
From: Jeffrey Walton <noloader@...il.com>
To: raju@...ux-delhi.org
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: stealing ssh keys

On Fri, Oct 26, 2012 at 10:49 PM, Raj Mathur (राज माथुर)
<raju@...ux-delhi.org> wrote:
> On Thursday 25 Oct 2012, Ivaylo Hubanov 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.
>
> We're splitting hairs here :) but the private key is actually used to
> encrypt.  That encryption is called a signature.
I hate to split hairs, but "encrypt with the private key" is not a
valid cryptographic transform.

> Except, what you encrypt with the private key is a digest of the
> message, not the whole message itself.
When you sign, you treat the hash as an instance of cipher text and
you perform the inverse transform - you are "decrypting with the
private key"

Jeff

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