| Idgarad 2007-08-06, 6:59 pm |
| I am working on a bit of a issue and I am hoping to find some
guidance.
Here is what I need to to:
I need to generate 2 SHA1 hashes (easy) based on an objects name and
it's DB id.
This is Easy so far and I have that down. I get 2 unique SHA1 hashes
stored.
Now depending on what I am doing I only need X number of bits out of
it. You see I am using the SHA1 hash as a unique pool of random bits I
am parsing. I need the first 8 for what type of effect I am going to
generate, the next 8 for how strong of an effect, and the next 8 for
how long the effects go for.
Now the question I have is how do I take a SHA1 hash and extract
certain segments of bits out of it via perl?
*** PART 2 ***
I am not a cryptographer by any measure but I am trying to do
something with unique content (can't get into details) where a user
has their own SHA1 hash and objects have their own.
What should I use to get a good pool of data by using the two together
(think.. ummm.. parents having a kid!)
Should I OR the bits, XOR the bits, or AND the bits? Lets assume that
more then 1 object can be used.
User
10110110...101010
Object 1
11101101...0000
Object 2
00100101....10010
etc..
I am leaning on XOR but I have to make sure that I have a good amount
of variance in the mix. I am hoping that using SHA1 against object
names and their DB id will prevent an all 0 and all 1 pool of bits.
And with XOR against concurrent SHA1 I am hoping not to end up with
all 0s and all 1s
|