4. Cont...
USES OF ENCRYPTION
• Protect information on your computer.
• Protect information in transit
• Confidentiality of medical, personal and transaction
records
• Email program
• Digital signature
7. Classical encryption techniques
• As opposed to modern cryptography
• Goals:
– To introduce basic concepts & terminology of
encryption
– To prepare us for studying modern cryptography
8. Basic terminology
• Plaintext: original message to be encrypted
• Ciphertext: the encrypted message
• Enciphering or encryption: the process of converting
plaintext into ciphertext
• Encryption algorithm: performs encryption
– Two inputs: a plaintext and a secret key
8
10. Cont...
• Deciphering or decryption: recovering plaintext from
ciphertext
• Decryption algorithm: performs decryption
– Two inputs: ciphertext and secret key
• Secret key: same key used for encryption and
decryption
– Also referred to as a symmetric key
11. Cont...
• Cipher or cryptographic system : a scheme for
encryption and decryption
• Cryptography: science of studying ciphers
• Cryptanalysis: science of studying attacks against
cryptographic systems
• Cryptology: cryptography + cryptanalysis
12. Ciphers
• Symmetric cipher: same key used for encryption and
decryption
– Block cipher: encrypts a block of plaintext at a
time (typically 64 or 128 bits)
– Stream cipher: encrypts data one bit or one byte at
a time
• Asymmetric cipher: different keys used for
encryption and decryption
12
13. Symmetric Encryption
• Conventional / secret-key / single-key
• Sender and recipient share a common key
• All classical encryption algorithms are symmetric
13
14. Symmetric Encryption
• Mathematically:
Y = EK(X)
X = DK(Y)
• X = plaintext
• Y = ciphertext
• K = secret key
or Y = E(K, X)
or X = D(K, Y)
• E = encryption algorithm
• D = decryption algorithm
• Both E and D are known to public
14
15. Classical Ciphers
• Plaintext is viewed as a sequence of elements
(e.g., bits or characters)
• Substitution cipher: replacing each element of
the plaintext with another element.
• Transposition (or permutation) cipher:
rearranging the order of the elements of the
plaintext.
• Product cipher: using multiple stages of
substitutions and transpositions
15
16. Caesar Cipher
• Earliest known substitution cipher
• Invented by Julius Caesar
• Each letter is replaced by the letter three positions
further down the alphabet.
• Plain: a b c d e f g h i j k l m n o p q r s t u v w x y z
Cipher: D E F G H I J K L M N O P Q R S T U V W X Y Z A B C
• Example: ohio state RKLR VWDWH
16
17. Caesar Cipher
a, b, c, ..., x, y, z
0, 1, 2, ..., 23, 24, 25
• Mathematically, map letters to numbers:
• Then the general Caesar cipher is:
c = EK(p) = (p + k) mod 26
p = DK(c) = (c – k) mod 26
• Can be generalized with any alphabet.
17
18. Objective
• The main Objective was to provide a Image
encryption mechanism which provides high security
level, less computational time and power in reliable
and efficient way to deal with balky, real time data.
• And Reduced the key size with equivalent efficient of
large key size.
19. Real life examples
• Online Banking
• E-commerce
• Student Records
• Health Records
• ATM Machines database
• Social Networking
• Bussinesses
20. Classify Security Attacks
• Passive attacks - eavesdropping on, or monitoring
of, transmissions to:
– obtain message contents, or
– monitor traffic flows
• Active attacks – modification of data stream to:
– masquerade of one entity as some other
– replay previous messages
– modify messages in transit
– denial of service
24. WHY IMAGE ENCRYPTION ?
• Nowadays, information security is becoming more
important in data storage and transmission.
• Images are widely used in different-different processes.
Therefore, the security of image data from unauthorized
uses is important.
• Image encryption plays a important role in the field of
information hiding.
• Image encryption method prepared information
unreadable. Therefore, no hacker or eavesdropper,
including server administrators and others, have access
to original message or any other type of transmitted
information through public networks such as internet
25. REQUIREMENTS OF IMAGE
ENCRYPTION
• Ability to get the pixels of the original image.
• Create a strong encryption image such that it cannot
be hacked easily.
• Faster encryption time such that encrypted image is
transferred faster to the person.
• Perfection in the original image we obtain after
decrypting it.
26. CHALLENGES IN IMAGE
ENCRYPTION
• The two main problems that arise in image encryption
process are with respect to:
• Computational time.
• Security level.
• Real time image encryption prefers ciphers that take
less amount of computational time without
compromising security.
27. Existing System
• There are traditional image encryption
techniques like DES, Triple-DES and IDEA.
• Limitations
o long computational time
o high computing power.
• Not suitable for practical image encryption
and for online communications
28. Applicability
• This encryption scheme is suitable for applications
like
Internet image encryption
secure transmission of confidential information in the
Internet.
29. Problem with conventional Methods
• Not suitable for practical image encryption , such as
on-line communication due to image features such
as:
• Bulk data capacity
• High correlation among pixels
• Non flexibility in performance characteristics and
level of security
• They may be susceptible to linear and differential
cryptanalysis
30. Exiting System
• Owner encrypts the original image using a standard
cipher with an encryption key.
• After producing the encrypted image, the content
owner hands over it to a data hider (e.g., a database
manager) and the data hider can embed some auxiliary
data into the encrypted image by losslessly vacating
some room according to a data hiding key.
• Then a receiver, maybe the content owner himself or
an authorized third party can extract the embedded
data with the data hiding key and further recover the
original image from the encrypted version according to
the encryption key
31. Disadvantages of Existing system
• All previous methods decrypted data by
reversibly from the encrypted images, which
may be subject to some errors on data
extraction and/or image restoration.
• It is difficult for data encrypted to reversibly
decrypt the data on an image.
33. Advanced Encryption Standard
• Proposed successor to DES
• DES drawbacks
– algorithm designed for 1970s hardware implementation
– performs sluggishly in software implementations
• 3DES is 3 times slower due to 3 rounds
– 64 bit blocksize needs to be increased to speed things up
• AES Overview
– 128, 192, 256 bit blocksize (128 bit likely to be most common)
– process entire block in parallel
– 128 bit key, expanded into 44, 32bit words with 4 words used for each
round
34. International Data Encryption
Standard (IDEA)
• Developed in Switzerland 1991
• 128 bit key, 64 bit blocksize, 8 rounds
• algorithm is quite different than DES,
– doesn’t use S-boxes
– uses binary addition rather than exclusive-or
• used in Pretty Good Privacy (PGP)
35. Blowfish
• 1993 – Bruce Schneier
• Popular alternative to DES
• Variable length keys - 128 bits but up to 448 bits
• up to 16 rounds
• 64 bit blocksize
• used in many commercial software packages
36. LITERATURE SURVEY
• Modified AES Based Algorithm for Image
encryption, 2007
• M. Zeghid, M. Machhout, L. Khriji, A. Baganne, and
R. Tourki
• Analyze the Advanced Encryption Standard (AES),
• Image encryption technique they add a key stream
generator (A5/1, W7) to AES
• For ensure improving the encryption performance.
37. Cont...
• Image Encryption Using Block-Based
Transformation Algorithm, 2008
• Mohammad Ali Bani Younes and Aman
Blowfish Encrypted image
• Block-based transformation algorithm based on the
combination of image transformation and a well
known encryption and decryption algorithm called
Blowfish.
38. Cont...
4 2
1 3 Blowfish image
•The original image was divided into blocks, which
were rearranged into a transformed image using a
transformation algorithm,
• Then the transformed image was encrypted using
the Blowfish algorithm
39. Cont...
• Results showed that the correlation between image
elements was significantly decreased.
• Their results also show that increasing the number of
blocks by using smaller block sizes resulted in a
lower correlation and higher entropy.
40. Cont...
• Image Encryption Using Self-Invertible Key Matrix
of Hill Cipher Algorithm, 2008
• Saroj Kumar Panigrahy, Bibhudendra Acharya and
Debasish Jena
• They are generating self-invertible matrix for Hill
Cipher algorithm.
• Using this key matrix they encrypted gray scale as well
as colour images.
• Their algorithm works well for all types of gray scale
as well as colour images except for the images with
background of same gray level or same colour.
41. Cont...
• An Image Encryption Approach Using a
Combination of Permutation Technique Followed
by Encryption, 2008
• Mohammad Ali Bani Younes and Aman Jantan
• Introduce a new permutation technique based on the
combination of image permutation and a well known
encryption algorithm called RijnDael.
• The original image was divided into 4 pixels × 4
pixels blocks
42. Cont...
• Which were rearranged into a permuted image using
a permutation process
• Then the generated image was encrypted using the
RijnDael algorithm.
• Their results showed that the correlation between
image elements was significantly decreased by using
the combination technique and higher entropy was
achieved
43. Cont...
• Image Encryption Using Advanced Hill Cipher
Algorithm, 2009
• Bibhudendra Acharya, Saroj Kumar Panigrahy, Sarat
Kumar Patra, and Ganapati Panda
• Proposed an advanced Hill (AdvHill) cipher
algorithm
• which uses an Involutory key matrix for encryption.
• They have taken different images and encrypted them
using original Hill cipher algorithm and their
proposed AdvHill cipher algorithm
44. Cont...
• And it is clearly noticeable that original Hill Cipher
can’t encrypt the images properly
• If the image consists of large area covered with same
colour or gray level.
• But their proposed algorithm works for any images
with different gray scale as well as colour images.
45. Cont...
• Digital image encryption algorithm based on
chaos and improved DES, 2009
• Zhang Yun-peng, Liu Wei, Cao Shui-ping, Zhai
Zheng-jun, Nie Xuan and Dai Wei-di
• In their technique firstly, new encryption scheme uses
the logistic chaos sequencer to make the pseudo-
random sequence, carries on the RGB
• This sequence to the image chaotically, then makes
double time encryptions with improvement DES.
• Their result show high starting value sensitivity, and
high security and the encryption speed.
46. Cont...
• Then makes double time encryptions with
improvement DES.
• Their result show high starting value sensitivity, and
high security and the encryption speed.
47. Cont...
• A Novel Image Encryption Algorithm Based on
Hash Function, 2010
• Seyed Mohammad Seyedzade, Reza Ebrahimi Atani
and Sattar Mirzakuchaki
• Proposed a novel algorithm for image encryption
based on SHA-512 hash function.
• The algorithm consists of two main sections:
48. Cont...
• The first does preprocessing operation to shuffle one
half of image.
• The second uses hash function to generate a random
number mask.
• The mask is then XORed with the other part of the
image which is going to be encrypted.
49. Cont...
• Digital Image Encryption Algorithm Based
Composition of Two Chaotic Logistic Maps, 2010
• Ismail Amr Ismail, Mohammed Amin, and Hossam
Diab
• Introduces an efficient chaos-based stream cipher,
composing two chaotic logistic maps and a large
enough external secret key for image encryption.
• In the proposed image encryption scheme, an external
secret key of 104 bit and two chaotic logistic maps are
employed to confuse the relationship between the
cipher image and the plain image.
50. Cont...
• Make the cipher more robust against any attack, the
secret key is modified after encrypting of each pixel
of the plain image.
• The robustness of the proposed system is further
reinforced by a feedback mechanism,
• Which makes the encryption of each plain pixel
depends on the key, the value of the previous cipher
pixel and the output of the logistic map (data
dependent property).
51. Cont...
• New modified version of Advance Encryption
Standard based algorithm for image encryption,
2010
• Kamali S.H., Shakerian R.,Hedayati M. and Rahmani
M
• Analysis Advance Encryption Standard(AES)
algorithm and present a modification to the Advanced
Encryption Standard (MAES) to reflect a high level
security and better image encryption..
52. Cont...
• Their result so that after modification image security
is high.
• They also compare their algorithm with original AES
encryption algorithm
53. Cont...
• Permutation based Image Encryption Technique,
2011
• Sesha Pallavi Indrakanti and P.S.Avadhani
• Proposes a new image encryption algorithm based on
random pixel permutation with the motivation to
maintain the quality of the image.
54. Cont...
• The technique involves three different phases in the
encryption process.
• The first phase is the image encryption.
• The second phase is the key generation phase.
• The third phase is the identification process. This
provide confidentiality to color image with less
computations Permutation process is much quick and
effective.
• The key generation process is unique and is a
different process
55. Cont...
• Image Security via Genetic Algorithm, 2011
• Rasul Enayatifar and Abdul Hanan Abdullah
• Proposed a new method based on a hybrid model
composed of a genetic algorithm and a chaotic
function for image encryption.
• In their technique, first a number of encrypted
images are constructed using the original image with
the help of the chaotic function.
56. Cont...
• In the next stage, these encrypted images are
employed as the initial population for starting the
operation of the genetic algorithm.
• Then, the genetic algorithm is used to optimize the
encrypted images as much as possible.
• In the end, the best cipher-image is chosen as the final
encryption image.
57. CONCLUSION
• In the digital world nowadays, the security of digital
images become more and more important
• Since the communications of digital products over
open network occur more and more frequently.
• In this presentation, we have surveyed existing work
on image encryption. We also give general guide line
about cryptography.
58. CONCLUSION
• We conclude that all techniques are useful for real-
time image encryption.
• Techniques describes in this research that can provide
security functions and an overall visual check, which
might be suitable in some applications.
• So no one can access image which transferring on
open network.
59. CONCLUSION
• In general, a well-studied, fast and secure
conventional cryptosystem should be chosen, surely
those algorithms, which provides higher security
60. References
• [1] S.S.Maniccam, N.G. Bourbakis, "Lossless image compression and
encryption using SCAN", Pattern Recognition 34 (2001),1229- 1245.
• [2] William stallings, ―Cryptography and Network Security: Principles &
Practices‖, second edition.
• [3]M. Zeghid, M. Machhout, L. Khriji, A. Baganne,R. Tourki, ―A
Modified AES Based Algorithm for Image Encryption‖, World Academy of
Science, Engineering and Technology 27 2007.
• [4] Mohammad Ali Bani Younes and Aman Jantan ―Image Encryption
Using Block-Based Transformation Algorithm‖ IAENG International
Journal of Computer Science, 35,2008.
61. References
• [5] Saroj Kumar Panigrahy, Bibhudendra Acharya and Debasish
Jen‖, Image Encryption Using Self-Invertible Key Matrix of Hill
Cipher Algorithm‖1st t International Conference on Advances in
Computing, Chikhli, India, 21-22 February 2008
• [6] Mohammad Ali Bani Younes and Aman Jantan, ―An Image
Encryption Approach Using a Combination of Permutation
Technique Followed by Encryption‖, IJCSNS International Journal
of Computer Science and Network Security, VOL.8 , April 2008.
• [7]Bibhudendra Acharya, Saroj Kumar Panigrahy, Sarat Kumar
Patra, and Ganapati Panda,‖ Image Encryption Using Advanced Hill
Cipher Algorithm‖, International Journal of Recent Trends in
Engineering, Vol. 1, No. 1, May 2009.
62. References
• [8] Zhang Yun-peng, Liu Wei, Cao Shui-ping, Zhai Zheng-jun, Nie
Xuan , Dai Wei-di,‖ Digital image encryption algorithm based on
chaos and improved DES‖, IEEE International Conference on
Systems, Man and Cybernetics, 2009
• [9] Seyed Mohammad Seyedzade, Reza Ebrahimi Atani and Sattar
Mirzakuchaki, ―A Novel Image Encryption Algorithm Based on
Hash Function‖ 6th Iranian Conference on Machine Vision and
Image Processing, 2010.
