Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-14 Thread Andy Isaacson
On Mon, Apr 12, 2004 at 06:00:26PM -0700, Joseph Ashwood wrote: From: Nicko van Someren [EMAIL PROTECTED] It's not clear to me that you need all this complexity. All you need if to arrange that the attacker does not know exactly what will be signed until it has been signed. So you

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-07 Thread R. A. Hettinga
--- begin forwarded text From: Nicko van Someren [EMAIL PROTECTED] Subject: Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases To: [EMAIL PROTECTED] Sender: [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] List-Id: Macintosh Cryptography mac_crypto.vmeng.com

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-06 Thread Zefram
R. A. Hettinga wrote: In practice you'll probably find something that you can alter in the last few hundred KB but still the raw processing cost will be a few orders of magnitude harder than a simple hash collision problem. [etc.] This disucssion suggests a simple countermeasure: put

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-05 Thread Arnold G. Reinhold
Dobbertin's 1996 collision demonstration is another good reason not to use md5, but is obviously hasn't gotten the open source community or Apple to stop. Whether my attack will be any more successful in effecting change remains to be seen. Publishing SHA1 hashes in parallel with md5 seems

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-05 Thread R. A. Hettinga
--- begin forwarded text From: Nicko van Someren [EMAIL PROTECTED] Subject: Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases To: [EMAIL PROTECTED] Sender: [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] List-Id: Macintosh Cryptography mac_crypto.vmeng.com

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-05 Thread R. A. Hettinga
--- begin forwarded text To: [EMAIL PROTECTED] From: Vinnie Moscaritolo [EMAIL PROTECTED] Subject: Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases Sender: [EMAIL PROTECTED] Reply-To: [EMAIL PROTECTED] List-Id: Macintosh Cryptography mac_crypto.vmeng.com

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-05 Thread Anton Stiglic
The attacks by Dobbertin on MD5 only allow to find collisions in the compression function, not the whole MD5 hash. But it is a sign that something might be fishy about MD5. MD5 output is 128 bits. There are two types of collision finding attacks that can be applied. In the first you are given

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-05 Thread Arnold G. Reinhold
At 4:51 PM +0100 4/5/04, Nicko van Someren wrote: ... While I agree that it is somewhat lax of Apple to be using MD5 for checking its updates it's far from clear to me that an attack of the sort described above would ever be practical. The problem is that the while there are methods for

Re: [Mac_crypto] Apple should use SHA! (or stronger) to authenticate software releases

2004-04-04 Thread Don Davis
hi, mr. reinhold -- there's stronger reason than the ones you cite, to distrust md5 as a message-digest. see these old sci.crypt threads, and the google-search below, for discussions of hans dobbertin's 1996 crack of md5: http://tinyurl.com/2ox7g http://tinyurl.com/3x446