[Bitcollider-commits] CVS: bitcollider/lib kztree.c,1.1,1.2

[Gordon M. <go...@us...>]

Update of /cvsroot/bitcollider/bitcollider/lib
In directory sc8-pr-cvs1:/tmp/cvs-serv15794/lib

Modified Files:
	kztree.c 
Log Message:
* kztree.c
    Better comment.

Index: kztree.c
===================================================================
RCS file: /cvsroot/bitcollider/bitcollider/lib/kztree.c,v
retrieving revision 1.1
retrieving revision 1.2
diff -C2 -r1.1 -r1.2
*** kztree.c	18 Jan 2004 10:59:54 -0000	1.1
--- kztree.c	18 Jan 2004 20:19:14 -0000	1.2
***************
*** 12,18 ****
   * Networks, 2004-01-16. 
   *
!  * Adapted to allow calculation in a stream fashion -- which
!  * helps calculate several hashes with only one pass through
!  * an input. 
   *
   * NOTE: A tree hash value cannot be calculated using a
--- 12,53 ----
   * Networks, 2004-01-16. 
   *
!  * A compact description of the process given by that code:
!  * 
!  *   Break the file into N 32KB segments. If N>0, MD5 each segment
!  *   separately yielding N 16-byte hash values.
!  * 
!  *   While N>2: Concatenate each neighbor pair of hash values
!  *   together, using the empty array in lieu of a partner if
!  *   necessary for the last value. MD5 each of these segments 
!  *   separately, giving (N+1)/2 16-byte hash values. Set N to 
!  *   this new total.
!  * 
!  *   N is now 0, 1, or 2. Concatenate remaining hash values together
!  *   into a final segment. MD5 this segment to give the final value.
!  * 
!  * Notable corner cases implied by the above: 
!  *   
!  *   For the zero-length input, the kztree value is the same as 
!  *   the MD5 value. 
!  * 
!  *   For input with length up to 32,768, the kztree value is the
!  *   MD5 of the MD5 of the input. 
!  * 
!  * Notable differences from THEX/TigerTree:
!  * 
!  *   (1) Leaf blocks are 32KB in kzhash rather than 1KB. 
!  *   (2) In kzhash, internal values with no sibling are rehashed, 
!  *       rather than promoted to the parent position unchanged as
!  *       in THEX. 
!  *   (3) Kzhash does not use a prefix byte to differentiate 
!  *       between leaf and inner-node hashes. 
!  *   (3) In kzhash, a file <= a single leaf block is hashed, then 
!  *       hashed again, preventing a trivial collision problem.
!  *       (THEX/TigerTree uses the leaf/node prefix bytes to 
!  *       prevent the collision.)
!  *
!  * The approach used here has been adapted to allow calculation in a 
!  * stream fashion -- which helps eliminate the need for multiple
!  * passes through a file when calculating several hashes at once.
   *
   * NOTE: A tree hash value cannot be calculated using a