passwd: added comment

diff --git a/loginutils/passwd.c b/loginutils/passwd.c
index a062596..c28e9b8 100644 (file)
--- a/loginutils/passwd.c
+++ b/loginutils/passwd.c
@@ -34,10 +34,15 @@ static void crypt_make_salt(char *p, int cnt)
 
        x += getpid() + time(NULL) + clock();
        do {
-               /* x = (x*1664525 + 1013904223) mod 2^32 generator is lame
+               /* x = (x*1664525 + 1013904223) % 2^32 generator is lame
                 * (low-order bit is not "random", etc...),
                 * but for our purposes it is good enough */
                x = x*1664525 + 1013904223;
+               /* BTW, Park and Miller's "minimal standard generator" is
+                * x = x*16807 % ((2^31)-1)
+                * It has no problem with visibly alternating lowest bit
+                * but is also weak in cryptographic sense + needs div,
+                * which needs more code (and slower) on many CPUs */
                *p++ = i64c(x >> 16);
                *p++ = i64c(x >> 22);
        } while (--cnt);