Related work Summary efficient algorithms for sorting and synchronization 1999
§3.6 Related work 68
data 16 bit
32 bit set
strength strength
Linux 16
32 Samba
16 30
Netscape 16
29
Table 3.6 : Fast signature effective bit strength
and the 16 bit fast signature hash. The fast signature is calculated once for each byte of literal data plus once per block and each fast signature is compared to the fast sig-
natures of each block from B so the number of pairwise comparisons of fast signatures is d
l
+ nLnL where d
l
is the number of bytes of literal data transferred. If a signa- ture algorithm has an effective bit strength of b then we would expect it to incorrectly
match approximately every 2
b
times, which means the effective bit strength is b
= log d
l
+ nLn Lm
where m is the observed number of incorrect matches. Table 3.6 shows the effective bit strengths for the three sets of results given in the previous table
27
. In all three test sets the 16 bit effective strength is the full 16 bits, which demon-
strates that the 16 bit hash is doing the job it was designed for. The performance of the 32 bit fast signature is not quite as good, but still does quite well considering the
simplicity of the algorithm.