17 Dec
2003
17 Dec
'03
11:17 p.m.
I agree; this cypher should definitely be handed a unique key each time it is used. However, you can do this pretty easily for file encryption, too.. Generate and store an "initialization vector" with each file of cyphertext. Instead of passing the user key directly to RC4, you instead pass a hash (MD5 or SHA) of the user key concatenated with the IV. If you don't have room to store the IV's, you could use some position-dependant information (e.g., per disk ID plus disk block number or file inode number) instead. - Bill