TuringPres.pdf
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Turing:
a fast software stream cipher
Greg Rose, Phil Hawkes
{ggr, phawkes}@qualcomm.com
25-Feb-03
Copyright © QUALCOMM Inc, 2002
DISCLAIMER!
•This
version (1.8 of TuringRef.c) is what we
expect to publish. Any changes from now on
will be because someone broke it. (Note: we
said that about 1.5 and 1.7 too.)
•This
is an experimental cipher.
Turing might
not be secure.
We've already found two
attacks (and fixed them). We're starting to get
confidence.
•Comments
are welcome.
•Reference
implementation source code
agrees with these slides.
25-Feb-03
Copyright© QUALCOMM Inc, 2002
slide 2
Introduction
•Stream
ciphers
•Design
goals
•Using
LFSRs for cryptography
•Turing
•Keying
•Analysis
and attacks
•Conclusion
25-Feb-03
Copyright© QUALCOMM Inc, 2002
slide 3
Stream ciphers
•Very
simple
–
generate a stream of pseudo-random bits
–
XOR them into the data to encrypt
–
XOR them again to decrypt
•Some
gotchas:
–
can’t ever reuse the same stream of bits
–
so some sort of facility for Initialization Vectors is important
–
provides privacy but not integrity / authentication
–
good statistical properties are not enough for
security… most PRNGs are no good.
25-Feb-03
Copyright© QUALCOMM Inc, 2002
slide 4
Turing's Design goals
•Mobile
phones
–
cheap, slow, small CPUs, little memory
•Encryption
in software
–
cheaper
–
can be changed without retooling
•Stream
cipher
–
two-level keying structure (re-key per data frame)
–
stream is "seekable" with low overhead
•Very
fast and simple, aggressive design
•Secure
(? – we think so, but it's experimental)
25-Feb-03
Copyright© QUALCOMM Inc, 2002
slide 5
Plik z chomika:
qfx
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