Design and Implementation of 4-bit Dynamic LFSRto Generate the Key Stream for Stream Ciphersin Cryptography

1. DESIGN AND IMPLEMENTATION
OF 4-BIT DYNAMIC LFSR
TO GENERATE THE KEY STREAM
FOR STREAM CIPHERS
IN CRYPTOGRAPHY

2. INTRODUCTION
With rapid development of computer and communication
networks, the secure information is being main objective of
this technology.
Random number generators (RNGs) play significant role for
this purpose. RNGs are generally useful insecurity purposes
systems like mobile communication, space communication,
bank security etc.

3. LFSR (Linear Feedback Shift Register)
 A linear feedback shift register takes a linear
function, typically an exclusive OR, as an
input.
 An LSFR, like other shift registers, is a
cascade of flip-flop circuits.
 The bits that change state for the others in
the cascade are called taps.

4. Applications of LFSR
 Uses as Counters
 Uses in Cryptography
 Uses in CircuitTesting
 Uses in Digital Broadcasting and
Communications

5. CRYPTOGRAPHY
 Cryptography is the study of secure
communications techniques that allow only
the sender and intended recipient of a
message to view its contents.

6. Pseudo Random Number
Generator
 A pseudorandom number generator (PRNG),
also known as a deterministic random bit
generator (DRBG) is an algorithm for
generating a sequence of numbers whose
properties approximate the properties of
sequences of random numbers

7. What to do with this
Randomness?
 Do statistical simulations
 Run security protocols
 Encrypt documents
 Use random numbers as key stream
 Analysis and Simulations

8. STREAM CIPHERS
 A stream cipher is a
symmetric key cipher
where plaintext digits
are combined with a
pseudorandom cipher
digit stream (key
stream).
 Each plaintext digit is
encrypted one at a time
with the corresponding
digit of the key stream,
to give a digit of the
cipher text stream.

9. ONE TIME PAD
 In cryptography, the one-time pad (OTP) is an
encryption technique that cannot be cracked,
but requires the use of a one-time pre-shared
key the same size as, or longer than, the
message being sent.
 A plaintext is paired with a random secret key
(also referred to as a one-time pad).

10. DESIGN PROPOSED

11. BASIC MODULES
 We are designing basic modules of flip flops,
Mux in order to build design for Dynamic
LFSR which further can be used as a module
to build proposed designs for key stream
generation for encryption of data/message.

12. FLIP FLOP

13. MUX

14. CONVENTIONAL EXTERNAL 4-BIT
LFSR

15. GRIFFEY DESIGN TO GENERATE KEY
STREAM
 As we have implemented basic modules and
dynamic LFSR now we are going to implement
the Griffey design to generate key stream
which can be used for encrypt/decrypt the
message at user/receiver end

16. SIMULATIONS AND ANALYSIS

18. THANK YOU