My plan is to bolster our existing Cryptography primitives to a minimally-usable level and implement a couple of new ones (CTR and Fortuna) using the PC book as my "specification". Having spent six months studying and implementing KryptOn (before I discovered the PC book), only to discover how little I still know about cryptography has led me to give up on becoming an expert and just doggedly and shrewdly follow the implementation advice in the PC book to the letter. Because of how well it is written, I *am* able to follow and implement their suggestions to the finest detail.
The primitive bolstering is now done. Next I plan to use these bolstered primitives to redo KryptOn one more time. The concept and interface of KryptOn will remain mostly the same, it is still intended to be an easy facade for common crypto problems. But the plan is base it *completely* on the recommendations in the PC book, with none of my own ideas in there.
I have a feeling, though, that the recommendation with respect to 2048-bit (asymmetric) keys may cause me to want to *allow* the KryptOn user to lax down to 1024-bit keys due to performance. Schneier and Ferguson say they are willing to sacrifice 90% performance for ideal security, but that may result in a system that is totally unusable.. We'll see..
- Chris
--- Ron Teitelbaum Ron@USMedRec.com wrote:
Nice work Chris.
Is anyone available to review and verify Chris's work? (Chris said: CFB should be verified)
Is anyone else able to help Chris with development?
Chris, I see your notes below; did you add those notes to the class comments?
Maybe you could coordinate more Schneier changes? Do you have a list of what changes you think we should be working on?
Maybe we could get some team work going?
Ron Teitelbaum
-----Original Message----- From:
cryptography-bounces@lists.squeakfoundation.org
[mailto:cryptography-bounces@lists.squeakfoundation.org]
On Behalf Of
Chris Muller Sent: Tuesday, March 07, 2006 11:39 PM To: cryptography@lists.squeakfoundation.org Subject: [Cryptography Team] BlockCipher mode
tests, fixes, enhancements
Hi, just a note to let you know of some
improvements
I've just committed to our repository.
Cryptography-Core
- All four BlockCipher modes are fixed-up and
working
(CFB should be verified).
- Added ability for BlockCiphers to encrypt and
decrypt arbitrary-length ByteArray's.
- When using the non-streaming cipher modes (CBC
and
CFB), proper padding of the ByteArray's should be
the
responsibility of the BlockCipher, not the user (developer). Therefore, #encrypt: applies the
"option
2" padding scheme specified by Ferguson and
Schneier
in 'Practical Cryptography', p. 68-69.
- Can also encrypt/decrypt from:to: positions in
an
existing ByteArray.
- Streaming modes (CTR and OFB) are supported as
stream ciphers, ByteArray's can be any size and no padding to the next-larger block is performed or needed.
Cryptography-Tests
- Created tests for all BlockCipher modes, by
generalizing the CTR test. They all now run the
same
(semi-robust) test.
- Separate test conditions ensure streaming modes
work
properly.
- Separate encrypt/decrypt ByteArray tests are
included for all BlockCipher modes.
More to come..
- Chris
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