Security Basics mailing list archives
RE: Encryption question
From: Gene LeDuc <Gene.LeDuc () tns-md com>
Date: Wed, 25 Feb 2004 12:45:12 -0500
Alice encrypts the message to Bob using Bob's public key and then signs it using her private key. Bob verifies that the message is from Alice by using her public key to check the signature and then decrypts the message with his private key. The encryption only hides the contents, it does not authenticate the message. The signing authenticates the message but does not hide the contents. You need both if you want to have a secure conversation. -----Original Message----- From: Preston, Tony [mailto:Tony.Preston () acs-inc com] Sent: Tuesday, February 24, 2004 11:01 AM To: security-basics () securityfocus com Subject: Encryption question 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? --------------------------------------------------------------------------- ---------------------------------------------------------------------------- --------------------------------------------------------------------------- ----------------------------------------------------------------------------
Current thread:
- Encryption question Preston, Tony (Feb 25)
- Re: Encryption question Lars Georg Paulsen (Feb 25)
- Re: Encryption question Hollis Johnson (Feb 26)
- Re: Encryption question Lars Georg Paulsen (Feb 26)
- Re: Encryption question Hollis Johnson (Feb 26)
- Re: Encryption question Jamie Pratt (Feb 25)
- RE: Encryption question Burton M. Strauss III (Feb 25)
- Re: Encryption question Aaron Keck (Feb 25)
- Re: Encryption question Theo Chaojareon (Feb 25)
- Re: Encryption question Raghu Chinthoju (Feb 27)
- <Possible follow-ups>
- RE: Encryption question Gene LeDuc (Feb 25)
- Re: Encryption question SERGIO OTERO (Feb 25)
- RE: Encryption question Jordan, Jason D. "Dallas" (Feb 25)
- RE: Encryption question Prasad S. Athawale (Feb 26)
- RE: Encryption question Hollis Johnson (Feb 26)
- Re: Encryption question Lars Georg Paulsen (Feb 25)