The "5 minutes" I mentioned doesn't implicitly refer to the amount of time needed to crack the ciphertext, but more the type of data and the amount of time it needs to be protected.
A couple examples: Example 1: A password which will only work for the next ten minutes only needs to be protected by encryption capable of rendering the text sufficiently scrambled for that 10 minute duration. This might mean it would take an attacker 1 minute to obtain the ciphertext and get it into a state where it can be cryptanalyzed. Four or five minutes to determine the cipher used. Then the attacker is left with only 3 or 4 minutes to break the cipher if they need one minute to actually use the password. So, how strong do you need encryption in this case? Only long enough to hold out against a 3 to 4 minute attack. Example 2: A "sealed" court case which is mandated to be sealed for 20 years needs to be protected by a cipher capable of using a large enough keyspace to keep a sustained attack against the data at bay for that 20 years. Herein lies the challenge in the practical utilization of cryptography... how do we know what will protect data for 20 years? We don't. So we make educated guesses. We make compromizes. We use "best-available". In the example of the password above, 56 bit DES would be a reasonable choice. It's fast, but weak - yet strong enough to keep that password encrypted for the two or three - heck, six, minutes it would be attacked. (this is not to say that one should use the weakest available cipher for any given problem set! 3DES, AES, or Blowfish would be a much better choice in any case.) In the example of the sealed court records, we're not worried about transaction speed or decryption speed so an asymmetric cipher capable of utilizing a 4096 bit (or larger!) private key is much more appropriate. Kind Regards, -dsp -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Arthur Chan Sent: Sunday, August 10, 2003 6:39 AM To: [EMAIL PROTECTED] Subject: Re: high-grade vs low-grade encryption with MD5 and DES This is really symptomatic of our industry, isn't it? We seen to be our own worse enemy. Back in 95, it took that French student days to crack the 40-bit codes. Now we are talking about minutes... its disheartening. Merde. I really wonder how some of those MS sites survive these days... ----- Original Message ----- From: "Dave Paris" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Monday, August 11, 2003 06:16 PM Subject: Re: high-grade vs low-grade encryption with MD5 and DES > "compromised" is probably a poor word to use, "pointlessly weak" is > more accurate. If you're going to use SSL and you're dealing with data > that needs to be protected longer than 5 minutes, use 128bit SSL. > > -dsp > > On Sunday, Aug 10, 2003, at 02:25 US/Eastern, Arthur Chan wrote: > > > Hi all. > > Verisign currently has a discount on both a high grade (128bits) SSL > > encrypted and a low grade (40bits) SSL encrypted certificates. The > > former is > > priced at US$895 and the latter at US$1395. > > I noticed some sites also present Verisign certificates with low-grade, > > 54-bits encryption from their Microsoft/IIS servers. However I cannot > > find a > > 54-bits certificate in > > www.verisign.com/products/site/commerce/index.html > > Is this 54-bits affair only for Microsoft / IIS ??? > > Is low-grade encryption with 40 and 54 bits considered "compromised" > > ??? > > Are there any finance/insurance industry standard requiring a 128 bits, > > high-grade encryption ??? > > > > ______________________________________________________________________ > > Apache Interface to OpenSSL (mod_ssl) www.modssl.org > > User Support Mailing List [EMAIL PROTECTED] > > Automated List Manager [EMAIL PROTECTED] > > > > ______________________________________________________________________ > Apache Interface to OpenSSL (mod_ssl) www.modssl.org > User Support Mailing List [EMAIL PROTECTED] > Automated List Manager [EMAIL PROTECTED] ______________________________________________________________________ Apache Interface to OpenSSL (mod_ssl) www.modssl.org User Support Mailing List [EMAIL PROTECTED] Automated List Manager [EMAIL PROTECTED] ______________________________________________________________________ Apache Interface to OpenSSL (mod_ssl) www.modssl.org User Support Mailing List [EMAIL PROTECTED] Automated List Manager [EMAIL PROTECTED]
