Is the 'crypt' function identical on Windows and *nix platforms?

No. See the thread starting at Re^2: replacing password in a file. Short: Many implementations use DES, but the libc is free to choose any other algorithm: http://pubs.opengroup.org/onlinepubs/9699919799/functions/crypt.html (<-- link is missing in that thread). Relevant quote:

The crypt() function is a string encoding function. The algorithm is implementation-defined.

Alexander