Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!watmath!clyde!cbatt!cbosgd!ihnp4!inuxc!inuxa!michel From: michel@inuxa.UUCP (Alan Michel) Newsgroups: net.crypt Subject: Re: Naieve Inquiry: Streaming Cyphers ( Message-ID: <189@inuxa.UUCP> Date: Wed, 30-Jul-86 22:41:18 EDT Article-I.D.: inuxa.189 Posted: Wed Jul 30 22:41:18 1986 Date-Received: Sat, 2-Aug-86 01:23:42 EDT References: <1065@ogcvax.UUCP> <25900002@okstate.UUCP> Organization: AT&T Consumer Products, Indianapolis Lines: 41 How about taking parts of the key, and generate two initial seed values for long psedo-random sequence generators in a pre-determined way. Then use bits from one sequence to indicate when to place a random bit into the data stream and the other random sequence (or even later bits in the same sequence) to indicate whether that random bit should be a 0 or a 1. If you wanted to do more padding than doubling the size of the file, or you want to do less than doubling it, then you could take n bits at a time from the first random sequence. If the n bits happens to be a particular binary value(s), you pad in a bit from the second sequence. Otherwise, you pass a data bit straight through. For example, to pad the file to 9/8ths its original size (or there-abouts) take the first random sequence 3 bits at a time, and if it is equal to a predetermined value (say 010) then pad a random bit in from the second (or the same) stream into the data. If it is not 010, then put a bit in from the actual message data stream. On decryption, you generate the same pseudo-random sequence, throw out the bits that land in the positions marked by the sequence as being random noise, and keep the bits marked as the message by the sequence for further decryption or use. For extra security, the amount and method of padding actually done should be previously agreed upon and treated as part of the key. Also, this should be combined with other forms of encryption as needed. The method of generating seed values from the keys should be such that if the seeds were somehow figure out, they would not easily lead back to the complete keys, especially if the same keys have been used to encrypt the data in the first place. WARNING - I know next to nothing about real world cryptography. This seems like an obvious and quick way to pad data, but I do not know how easy it is to crack, or how much it may really increase/decrease security. Just a thought. Any comments?