crypt is a very weak encryption program that should no longer be used. This was actually true 25 years ago. At this point, crypt is sadly obsolete. You need a strong encryption algorithm and one of the best currently available is AES-256. No one has broken it yet. The US government currently allows the use of AES-256 to protect Top Secret information.
I suggest that you use gpg to encrypt your file, but you must specify the encryption algorithm like this:
gpg -c --cipher-algo aes256 secret.txt
and to decrypt the file:
gpg secret.txt.gpg
GNU Privacy Guard, gpg, seems to simply come with our Linux systems. It is available on sunfreeware.com for Solaris. I also found a package for XP at the
The GNU Privacy Guard - GnuPG.org site (navigate to the download page).