Information Technology Reference
In-Depth Information
a) Collision Resistant Hash Function[16]: A collision resistant hash function is a
function which takes a variable length input and produces a fixed length output
with the property that even slightest change in the input will reflect change in the
output(hash value). The input to hash function is called a message and the output
is known as hash value.
The collision resistant hash function exhibits the following four properties:
It should be easy to compute hash value for any message.
It should be infeasible to deduce the message from the hash value. This is known
as one way property.
It should be infeasible to find two different messages say m1 & m2 with same
hash value. This property is known as collision resistance.
It should be infeasible to change a message without reflecting any change in it's
hash value.
This kind of hash function has many applications such as digital signature, MAC etc.
b) Block Cipher : It is one of the most important primitives of various cryptographic
algorithms & protocols like MAC & various hash functions. It is used mainly to
provide confidentiality of data. Block cipher works on fixed length inputs known
as blocks. These ciphers encrypt or decrypt one block of data at a time.
Some of the most widely used block ciphers are DES (Data Encryption
Standard), 3DES (Triple DES) and AES (Advanced Encryption Standard).
c) Stream Cipher : It is another most important & common primitives for various
cryptographic algorithms. In this case, the encryption or decryption of data takes place
one bit at a time. Thus it can be treated as a block cipher with block size of 1 bit.
Some of the most commonly used stream cipher algorithms are ORYX,
SEAL & RC4.
d) Transformation Function: Transformation function is any simple mathematical
function which can be applied to an integer. Here the transformation function is
applied on the nonces to avoid replay attacks.
5
The Proposed Security Protocol : Zero Knowledge Password
Authentication Protocol (ZK-PAP)
As in general scenario, every user has a username & password used to login to a
system to access various resources. The password is secret to the user which only he
can change when logged in to the application and the same change is registered with
the server.
The simple version of the algorithm provides only one way authentication, that is,
only server can authenticate a client system. Let us designate the server and client as
verifier and prover for ease of understanding.
The protocol is initiated by the prover by sending his username and a
challenge(nonce) N1 to the verifier in clear. The verifier responds by generating a
random session key, say k and another challenge(nonce) N2. Then it concatenates N1,
Search WWH ::




Custom Search