|
|
Electronic File Transfer
Many products, like our Encrypt-It, build extensive file validation checks into the file structure of the encrypted file. If any character of the encrypted data is EVER changed, you are notified! The implications are discussed in the following paragraphs.
Our extensive checks means you can have complete confidence that the decrypted data is ALWAYS exactly what you started with. However, there is a drawback. You need to be aware of the limitations of the electronic transfer medium you use. If the file transfer alters the original file in ANY way, Encrypt-It will flag this as an attempt to alter your data. In essence it really is, but it may just reflect the limitations of the electronic transfer medium you are using.
When you transfer files by floppy diskette, preservation of the original size and contents without error are virtually guaranteed. The same cannot be said about electronic transfer of data via bulletin boards and information services like CompuServe, AOL, or GEnie. Our suggestions for electronic file transfer are:
1. Use ZModem protocol whenever possible. Kermit may also maintain the correct file size, but we are unsure of other protocols. A problem with XModem is that it adds bytes to round the file size up to the next higher block size. Check your file transfer protocol to make sure it does not add additional characters to pad the transferred data out to a standard block size.
2. Wherever possible use binary file transfer. Some information services convert your file into a limited range ASCII message and insert it into an email message. It is up to the end user to translate the file back into its initial state. This can be confusing and may not totally ensure the integrity of your data. Watch out for this.
3. ALWAYS use error correction if it is an option. Implementations of ZModem frequently offer the option of using a 32 bit CRC, use this whenever possible. If a file is ever altered during transfer, our Encrypt-It will flag it as a modification of your data! This includes any attempt to add or delete characters!