Re: Re: method of ID'ing

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Re: Re: Re: method of ID'ing by tachyon (Chancellor) on Apr 13, 2002 at 22:11 UTC
So they say. Check out the unofficial MD5 homepage here or read the full RFC1321 cheers tachyon s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print	[reply]
Re: Re: Re: Re: method of ID'ing by ariels (Curate) on Apr 14, 2002 at 10:25 UTC
An MD5 collision is known, for particular values of "known". This is probably not an issue for the average web-based script, though.	[reply]
Re: Re: Re: Re: Re: method of ID'ing by tachyon (Chancellor) on Apr 14, 2002 at 12:41 UTC
Thanks for the info, certainly news to me! SDK rule 1: There is always an unforseen edge case. According to Sod's law (Sod reckonned Murphy was an optimist) this edge case will of course cause the worst possible problem, which will naturally occur at the worst possible moment and have the most catastrophic effects....am I a jaded cynic? The probability appears rather low Here is a good link on hashing functions on the RSA site cheers tachyon s&&rsenoyhcatreve&&&s&n.+t&"$'$`$\"$\&"&ee&&y&srve&&d&&print	[reply]
Re: Re: Re: method of ID'ing by ilcylic (Scribe) on Apr 15, 2002 at 01:01 UTC
It has a one to (one of 2 to the 128th) possible values. Since the output domain of MD5 is limited to a 128 bit string, it is possible for more than one value to map to the same output value. It is a very small chance that two of the given inputs would ever map to the same string (unless there were a statistically significant percentage of 2^128 worth of entries) and even if there were, I don't believe this code is being used for something which is intended to be mission critical. Another issue to consider with MD5 is that the input value needs to be fairly large, if you're using it for 'important' purposes. Since MD5 operates on strings of size evenly divisible by 512, and pads otherwise, it's important to make sure you have at least one full block, to retain computational protection. Hope that helped. -il cylic	[reply]