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- How to share a
secret: Commun. ACM,
Vol. 22, No.
11. (November
1979), pp.
612-613.
Source: Commun. ACM, Vol. 22, No. 11. (November 1979), pp. 612-613. - Two Remarks on
Public-Key
Cryptology: (2000)e key in
previous
epochs. In
1997 I
proposed the
obvious
extension to
digital
signatures, in
order to
prevent the
retrospective
forgery of
messages
signed using
keys belonging
to earlier
epochs but
without
requiring that
the public key
infrastructure
accommodate
large numbers
of
time-limited
public keys.
As motivation,
note that
while
Di#e-Hellman
key exchange
[6] can
provide
forward
security
easily in
interactive
communication,
the US Defense
Messaging
System (DMS)
apparently
uses
transient...
Source: (2000) - MAC
Reforgeability: (10 Mar
2006)Message
Authentication
Codes (MACs)
are central
algorithms
deployed in
virtually
every security
protocol in
common usage.
In these
protocols, the
integrity and
authenticity
of messages
rely entirely
on the
security of
the MAC; we
examine cases
in which this
security is
lost. In this
paper, we
examine the
notion of
reforgeability
for MACs. We
first give a
definition for
this new
notion, then
examine some
of the most
widely-used
and well-known
MACs under our
definition. We
show that for
each of these
MACs there
exists an
attack that
allows
efficient
forgeries
after the
first one is
obtained, and
we show that
simply making
these schemes
stateful is
usually
insufficient.
For those
schemes where
adding state
is effective,
we go one step
further to
examine how
counter misuse
affects the
security of
the MAC,
finding, in
many cases,
simply
repeating a
single counter
value yields
complete
insecurity.
These issues
motivated the
design of a
new scheme,
WMAC, which
has a number
of desirable
properties. It
is as
efficient as
the fastest
MACs, resists
counter
misuse, and
has tags which
may be
truncated to
the desired
length without
affecting
security
(currently,
the fastest
MACs do not
have this
property),
making it
resistant to
reforging
attacks and
arguably the
best MAC for
constrained
environments.
Source: (10 Mar 2006) - Slid Pairs in
Salsa20 and
Trivium: (23 Sep
2008)The
stream ciphers
Salsa20 and
Trivium are
two of the
finalists of
the eSTREAM
project which
are in the
final
portfolio of
new promising
stream
ciphers. In
this paper we
show that
initialization
and key-stream
generation of
these ciphers
is , i.e. one
can find
distinct (Key,
IV) pairs that
produce
identical (or
closely
related)
key-streams.
There are
$2^256$ and
more then
$2^39$ such
pairs in
Salsa20 and
Trivium
respectively.
We write out
and solve the
non-linear
equations
which describe
such related
(Key, IV)
pairs. This
allows us to
sample the
space of such
related pairs
efficiently as
well as detect
such pairs in
large portions
of key-stream
very
efficiently.
We show that
Salsa20 does
not have
256-bit
security if
one considers
general
birthday and
related key
distinguishing
and
key-recovery
attacks.
Source: (23 Sep 2008) - Merkle Puzzles
are Optimal: (23 Jan
2008)We prove
that every key
exchange
protocol in
the random
oracle model
in which the
honest users
make at most n
queries to the
oracle can be
broken by an
adversary
making O(n^2)
queries to the
oracle. This
improves on
the previous
Omega(n^6)
query attack
given by
Impagliazzo
and Rudich
(STOC '89).
Our bound is
optimal up to
a constant
factor since
Merkle (CACM
'78) gave an n
query key
exchange
protocol in
this model
that cannot be
broken by an
adversary
making o(n^2)
queries.
Source: (23 Jan 2008)
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