Given you are on AIX, you could try https://secure.wikimedia.org/wikiped...ypt_%28Unix%29
, although I'm not sure how strong it would be as per the article.
Best to read the man page for crypt on your system.
Alternatives may include gpg http://linux.die.net/man/1/gpg
, openssl http://linux.die.net/man/1/openssl
, but they may not be installed.
Best guess is to read the man page for crypt and to look at the bottom where it may reference other related tools/cmds.
Also, try to google 'AIX encrypt' or similar.