TuringPres.pdf

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Turing:

a fast software stream cipher

Greg Rose, Phil Hawkes

{ggr, phawkes}@qualcomm.com

25-Feb-03

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

slide 2

Introduction

•Stream

ciphers

•Design

goals

•Using

LFSRs for cryptography

•Turing

•Keying

•Analysis

and attacks

•Conclusion

25-Feb-03

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

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

slide 5

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TuringPres.pdf

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