Re: Encryption question

From: SERGIO OTERO (SOTERO_at_gire.com)
Date: 02/25/04

  • Next message: Burton M. Strauss III: "RE: Encryption question" 
    Date: Wed, 25 Feb 2004 18:02:17 -0300
To: <Tony.Preston@acs-inc.com>, <security-basics@securityfocus.com>

    You're describing a man in the middle attack. Using digital certificates prevents this kind of trouble. Since the CA "authenticates" the certificate owner (i.e. Alice or Bob) and digitally signs the user certificate, you can't fake Alice nor Bob identity.

    Hope this help.

    >>> "Preston, Tony" <Tony.Preston@acs-inc.com> 24-02-04 04:01:29 >>>

    Tony Preston
    Systems Engineer, AS&T Inc.
    Division of L3 Corporation
    (609) 485-0205 x 181

    I have what is a rather basic question... I probably am missing something
    so I thought I would ask here.

    Alice and Bob both have a public and private key.

    Alice encrypts her email to Bob using his public key. Sends the email and
    Bob decrypts it using his keys..

    Since both Bob and Alice's public keys are known, Why can't I take Alice's
    public key and create a key pair using any other private key. Now, I fake
    an electronic signature from Alice using the pair I created and send a bogus
    encrypted message to Bob with my "fake" Alice signature. Bob checks the
    signature by using the public key and it is valid. Bob assumes the message
    is from Alice...

    What prevents me from spoofing someone's electronic signature this way?

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  • Next message: Burton M. Strauss III: "RE: Encryption question"

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