makekey improves the usefulness of encryption schemes that depend on a key by increasing the amount of time required to search the key space. It attempts to read 8 bytes for its key (the first eight input bytes), then it attempts to read 2 bytes for its salt (the last two input bytes). The output depends on the input in a way intended to be difficult to compute (that is, to require a substantial fraction of a second).
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. The salt characters 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 4,096 cryptographic machines all based on the National Bureau of Standards DES algorithm, but broken in 4,096 different 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 output key bits in the result.
makekey is intended for programs that perform encryption. Usually, its input and output will be pipes.
makekey can produce different results depending upon whether the input is typed at the terminal or redirected from a file.