S/Key implementation question

["W. Stockwell" <waldo@antisocial.net>]

Just out of curiosity I've been looking at the implementation of S/Key.  I
have been unable to figure out what purpose this function has:

/* Make sure line is all seven bits */
void
sevenbit(s)
	char *s;
{
	while (*s)
		*s++ &= 0x7f;
}

It's called with the seed and pass phrase passed to i before it is passed
through the hash algorithm.  What function does this serve?  I haven't
been able to identify anything in the related rfc (1938).  Can someone
give me an idea?

Please reply to me as I am not a normal list subscriber.

Will Stockwell
waldo@antisocial.net
www.antisocial.net