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which means that the Sender and the Receiver provide all
the transcripts of the message in the deniable authentication
protocol to them.
If DAP satisfies the condition one and four in:
Inj-event (whole sender (Receiver, x)) = inj-event(whole Receiver (Sender, x) )
Inj-event (whole Thirdparty (Receiver, x)) = inj-event(whole Thirdparty (Sender, x) )
Definition DAP and DAP’ satisfies the correspondence and
with public variables V = φ, then DAP is a secure deniable
authentication protocol with session in a adversary model in
strong deniability. In the above definition of DAP the
injective correspondence can be instead by non-injective
correspondence.
Weak deniability:
The purpose of weak deniability is to protect the privacy of
Sender. After execution of the deniable authentication
protocol the Receiver can prove to have spoken to Sender
but not the content of what the Sender authenticated in a
way that the Receiver cannot convince a third party.
Deniable Authentication Protocol
Security Properties
Active Adversary Model
Sanjay Kumar Sonkar et al ,Int.J.Computer Technology & Applications,Vol 3 (2), 525-531
Relating the Two Models:
Meng & Shao
Mechnized Model
Automated
Verification
ISSN:2229-6093
In order to prove any relationship between the formal and
computational worlds, we need to define the interpretation
of expressions [8] and patterns. Once an encryption scheme
is depicted, we can define the interpretation function α,
which assigns to each expression or pattern M a family of
random variables {α η (M)} η∈ N such that each α η (M) takes
values in strings. For expressions:
Blocks are interpreted as strings,
Each key is interpreted by running the key
generation algorithm,
Pairs are translated into computational pairs,
Formal encryptions terms are interpreted by
running the encryption algorithm.
Difference between Formal approach and
Computational approach [15]:
Formal approach Computational
approach
Message Terms Bits-strings
Encryption Idealized Algorithm
Adversary Idealized Any polynomial
algorithm
Secrecy Reach ability-based Indistingability
property property
Guarantees Unclear Strong
Proof Automatic By hand and errorprone
Balnchet Calculus
Computational Model
Crypto Verification
Figure 2: Model of automatic verification of deniable authentication
protocols
If the Receiver want to prove that the Sender have
authenticated messages to Receiver, he must provide the
evidence related to the thing. An adversary model in weak
deniability: When discussing the weak deniability, in
addition the adversary has the ability in previous section; we
always suppose that only the Receiver generates the
evidence that the Sender have authenticated messages to
Receiver. Receiver cannot get the secret information of the
Sender, for example the private key of Sender. Receiver can
provide his secret information to the Third party.
If DAP’ satisfies the condition one in definition DAP and
DAP’ satisfies the correspondence:
Inj-event (whole sender (Receiver, x)) = inj-event(whole Receiver (Sender, x) )
Inj-event (whole Thirdparty (Receiver, x)) = inj-event(whole Thirdparty (Sender, x) )
and with public variables V = φ, then DAP is a secure
deniable authentication protocol with session functions in a
adversary model in weak deniability. In the above definition
of DAP the injective correspondence can be instead by noninjective
correspondence.
Our Contribution:
The primary contribution of this paper is that it tried to bring
about various concepts which are requisite for concrete
development in proofs of cryptography protocols and
remove the bottleneck reason for its failure. In particular, we
define the equivalence between formal messages in the
presence of both key cycles and secret shares, and then
prove the computational soundness [13][16] about formal
encryption in this setting.
1. First computational analysis of an industrial protocol:
Consider authentication[29] and secrecy
properties[26],
Analyzed Basic Kerberos 5 and public-key
Kerberos[22],
Kerberos is complex (e.g. PKINIT uses both
public-key and symmetric).
Cryptographic primitives (Encryption, Signatures,
MACs).
2. Proofs were carried out symbolically in the BPW
model:
Proofs in Dolev-Yao style model are
cryptographically sound,
Proofs can be automated.
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