Re: Randomly-generated challenge method ?

From: Gregory G Rose (ggr_at_qualcomm.com)
Date: 10/19/05 

Date: 19 Oct 2005 10:54:12 -0700

I guess I'm misunderstanding what you're trying to
do here. See comments below.

In article <mn.9b967d5a54f8c207.18740@invalid.net>,
O.L. <nowhere@invalid.net> wrote:
>I thought about a secure method of authentication based on a simple
>password (memorizable by a human).
>This method uses hazard to increase the authentication process
>duration, and so to prevent attackers from quickly break the encryption
>by brute force. The computation duration can be easily set by
>increasing or decreasing the challenge string length.
>
>1) The user sends his password (ie: "azerty") to the server

Isn't this the real problem? The user just sent
his cleartext password... any eavesdropper now
knows it.

>2) The server get the password, and complete it to a length of 128 bits
>(16 chr), with characters extracted randomly from the password string.
>(ie: azertyrzayeerayz), and finally send his MD5 hash to the user.

But the server hasn't checked that the password is
correct? So in what sense is this an
authentication method?

[rest snipped]

It does bear an interesting relationship to
Merkle's Puzzles, the precursor to public key
encryption.

Greg. 

-- 
Greg Rose
232B EC8F 44C6 C853 D68F  E107 E6BF CD2F 1081 A37C
Qualcomm Australia: http://www.qualcomm.com.au

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