MAKEKEY(8) System Manager's Manual MAKEKEY(8)
makekey - generate encryption key
Makekey improves the usefulness of encryption schemes depending on a
key by increasing the amount of time required to search the key space.
It reads 10 bytes from its standard input, and writes 13 bytes on its
standard output. The output depends on the input in a way intended to
be difficult to compute (i.e. to require a substantial fraction of a
The first eight input bytes (the input key) can be arbitrary ASCII
characters. The last two (the salt) are best chosen from the set of
digits, upper- and lower-case letters, and `.' and `/'. The salt char‐
acters are repeated as the first two characters of the output. The
remaining 11 output characters are chosen from the same set as the salt
and constitute the output key.
The transformation performed is essentially the following: the salt is
used to select one of 4096 cryptographic machines all based on the
National Bureau of Standards DES algorithm, but modified in 4096 dif‐
ferent ways. Using the input key as key, a constant string is fed into
the machine and recirculated a number of times. The 64 bits that come
out are distributed into the 66 useful key bits in the result.
Makekey is intended for programs that perform encryption (e.g. ed and
crypt(1)). Usually its input and output will be pipes.