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- Path: sparky!uunet!utcsri!torn!cunews!revcan!micor!uuisis!tanda!marc
- From: marc@tanda.isis.org (Marc Thibault)
- Reply-To: marc@tanda.isis.org
- Newsgroups: sci.crypt
- Subject: multi-algorithm encryption
- Message-ID: <322769441D5.61R.123518000@tanda.isis.org>
- Date: Thu, 13 Aug 92 18:33:19
- Distribution: world
- Organization: Thibault & Friends
- Lines: 38
-
-
- Ok - assuming everybody gets a kick at the can -here's mine.
-
- A search of the literature has unearthed countless references
- to the fact that secret algorithms are out, but no reference
- to an encryption that uses many (known) algorithms, selected
- by the key.
-
- Assume two reasonably large sets of functions F and G, such
- that Gi reverses Fi for any i. These can be any sort of
- reversible function that operates on a small piece of data
- (eg. a byte). The encryption works as follows:
-
- 1) Use one-way hashes of an arbitrarily long key to produce
- two cryptographically strong keys M and N (A variant of MD5
- that produces longer output?).
-
- 2) Subject the compressed plaintext to a random stub,
- substitution and transposition based on M and/or N to
- complicate a plaintext attack. This produces string D.
-
- 3) Generate E. For each Ei, apply the algorithm from F
- selected by key fragment Mi. Something like
-
- Ei = (F(Mi))(N,D,i,E)
-
- 4) Back out step 2. I'm not sure why, but every scheme I've
- seen does this.
-
- Decryption uses G instead of F and runs i backward.
-
- This description begs the issues relating to key and block
- lengths, since any scheme can be improved by increasing them.
- The question is, all else being equal, is this an improvement
- over more conventional approaches?
-
- ,Marc
-
-
- --
- Marc Thibault | | Any Warming,
- marc@tanda.isis.org | Oxford Mills, Ontario | Global or otherwise,
- CIS:71441,2226 | Canada | appreciated.
-
-