randomly order a list

Dar Scott dsc at swcp.com
Fri Jun 7 18:05:22 EDT 2013


For we mere mortals, I suspect that the social and physical aspects of security dominate and the infinitesimal increase in application speed from using the faster functions might in some mysterious way do more for our security than a better hash.  But, also, being one of the mere mortals, I can't really say anything on the subject.  

So, I lean toward what the experts recommend, but md5 and sha1 are good hashes and they are readily available.  They are usually not the weakest link in our security.  Given that, if sha256 is needed, there are several approaches to getting it done in LiveCode.

Dar


On Jun 7, 2013, at 10:13 AM, Geoff Canyon wrote:

> I did some reading and it sounds like md5 and sha1 should both be
> deprecated in favor of sha256.
> 
> 
> On Fri, Jun 7, 2013 at 10:57 AM, Dar Scott <dsc at swcp.com> wrote:
> 
>> Right.  There is a little bit of overhead for padding for both md5 and
>> sha1 (they use the same padding method), as a string a multiple of 64-bytes
>> is created.  Then each resulting 64-byte block is processed; this is
>> linear.  The methods are very similar, an important difference being the
>> number of 32-bit chaining variables; md5 has four and sha1 has five.  (The
>> final values are the hash.)  That is a factor in making the sha1 basic
>> operation take longer, and thus the whole process take longer.  (We could
>> look it up and count all the XOR, SHIFT, OR and AND operations, but you can
>> imagine there would be more in scrambling five things instead of
>> four--well, scrambled along with a portion of the block.)
>> 
>> I empathize your arrrgh.
>> 
>> Dar
>> 
>> 
>> 
>> On Jun 7, 2013, at 9:18 AM, Geoff Canyon wrote:
>> 
>>> On Wed, Jun 5, 2013 at 5:14 PM, Alex Tweedly <alex at tweedly.net> wrote:
>>> 
>>>> Your code has a minor bug :-)
>>>> 
>>>> You "get MD5Digest(S[1]) "
>>>> instead of using   S[i]
>>>> 
>>> 
>>> 
>>> Arrrrrrrrgh!!! ;-)
>>> 
>>> Interestingly, md5 appears to scale roughly linearly on the length of the
>>> strings. 100x as long string means about 15x as long to md5, while 1000x
>> as
>>> long string means about 120x as long to md5. sha1 is longer but scales
>>> similarly.
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