You need to change your key frequently to limit the number of files that can be decrypted if the key is compromised.
Encryption and decryption keys can be entire sentences like "My dog is brown.".  Your aren't limited to meaningless short groups of characters.
You can encrypt a file using the registered version of Encrypt-It with the proprietary level and a person using the shareware version can decrypt it.
You can coordinate an initial key in person between two groups.  Then use that key to wrap passing normal encryption/decryption keys between the two groups thereby preventing compromise of the new keys.
The proprietary level of encryption built into Encrypt-It is very safe for normal data because it uses multiple different encryption layers.
The Data Encryption Standard (DES), RSA, and other encryption methods can be broken but only at a cost normally far exceeding the value of the data being protected.
Each file in Encrypt-It would have to be broken one at a time.  Each file is unique and breaking one does not compromise any other encrypted file.
If you encrypt file A to file B, then encrypt file A again to file C, files B and C are totally different but both will decrypt back to file A.  We add random data during encryption.
If anyone ever alters a single bit in an encrypted file you will be notified.  The file structure contains embedded CRCs to guard against your data being altered without you being notified.
Encrypted files can't be compressed.  If you want to send a file electronically be sure to compress/archive it first then encrypt it in that order.
Once you encrypt a file, the file's contents are totally protected.  Anyone can view the encrypted file but its contents will look like total garbage to them.
Email can be viewed at numerous points in its path to the intended destination.  Encryption is one of the few methods that can protect email from being viewed by unauthorized people.