Main Project Slides

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Submitted by

P. Arun Goud (08W81A0401)

M. Bhanu Prasad (08W81A0406)

U. Jagadeeswar (08W81A0416)C. Praveen Kumar (08W81A0430)

I . Sharath Chandra N. Narasimha

M .Tech M. Tech



Cryptography:

“Cryptography is the study of mathematical

techniques related to aspects of informationsecurity such as confidentiality, data integrity,entity authentication, and data originauthentication.

Cryptography is not the only means ofproviding information security, but rather one setof techniques.”



Cryptographic goals:

Privacy or confidentiality

Data integrity

Authentication

Non-repudiation



Cipher: A cipher is any method of encrypting text

(concealing its readability and meaning). It is alsosometimes used to refer to the encrypted text messageitself.

Types of cipher:

1.Block cipher 2.Stream cipher



What is AES.?

AES is a symmetric encryption algorithm

processing data in block of 128 bits.

AES may configured to use different key-lengths,

the standard defines 3 lengths and the resultingalgorithms are named AES-128, AES-192 and AES-256

respectively to indicate the length in bits of the key.



What is DES.?

DES is the archetypal block cipher an algorithm

that takes a fixed-length string of plain text bits and

transforms it through a series of complicated

operations into another cipher text bit string of thesame length.



Key size:In cryptography key size or key length is the

size measured in bits of the key used in a

cryptographic algorithm (such as a cipher). An

algorithm's key length is distinct from its

cryptographic security, which is a logarithmic measureof the fastest known computational attack on the

algorithm, also measured in bits.



Significance of key:

Keys are used to control the operation of a cipher

so that only the correct key can convert encrypted textto plaintext.

A key should therefore be large enough that a bruteforce attack is infeasible



Key Generation:

Key generation is the process of generating keys

for cryptography. A key is used to encrypt and decrypt whatever data is being encrypted / decrypted.

steps of key generation:

1. Rotate word step 2. The sub byte step



AES Key Generation:

Plain Text Cipher Key

SubByte

Shift Row

Mix Column

SubByte

ShiftRow

Cipher Text

Key Schedule

---------------------------------------------------------------------------------

128 cipher text

Round Key 1~Round key 9128

128

Round Key 10Round Key 10

Round Key 1~Round key 9



Rotate word step:Key Length = 4, 6, 8

Cipher Key = 2b 7e 15 16 28 ae d2 a6 ab f7 15 88 09 cf 4f 3c

2b 7e 15 16 28 ae d2 a6 ab f7 15 88 09 cf 4f 3c

W 0

W1 W2 W3

ROTATE WORD()

7e 15 16 2b ae d2 a6 28 f7 15 88 ab cf 4f 3c 09

Number of Rounds = 10, 12, 14

AES -128, 192, 256



Sub bytes step:

F



Rcon ROM operation:



DES KeyGeneration:



DES Modes of Operation:

ECB ( Electronic code block )

CBC (Cipher block chaining) CFB ( Cipher feedback )

OFB ( Output feedback )



Electronic code block (ECB):

o This is the regular DES algorithm in which Data isdivided into 64-bit blocks and each block is encrypted

one at a time.

o Separate encryptions with different blocks are totallyindependent of each other.



Cipher block chaining (CBC):

In this mode of operation, each block of ECB

encrypted cipher text is XOR-ed with the nextplaintext block to be encrypted, thus making all theblocks dependent on all the previous blocks.

This means that in order to find the plaintext of aparticular block, you need to know the cipher text,the key, and the cipher text for the previous block.



Cipher feedback (CFB):

In this mode, blocks of plaintext that are less than

64 bits long can be encrypted.

Normally, special processing has to be used tohandle files whose size is not a perfect multiple of

8 bytes, but this mode removes that necessity .



Output feedback (OFB): This is similar to CFB mode, except that the cipher text

output of DES is fed back into the Shift Register, rather

than the actual final cipher text.

The Shift Register is set to an arbitrary initial value,and passed through the DES algorithm.

The output from DES is passed through the M-box andthen fed back into the Shift Register to prepare for thenext block.



Comparison of AES and DES:

Advanced Encryption Standard not only assures securitybut also improves the performance in a variety of settings

such as smartcards, hardware implementations etc.

AES is federal information processing standard and thereare currently no known non-brute-force direct attacksagainst AES.

AES is strong enough to be certified for use by the USgovernment for top secret information



DES performs lots of bit manipulation in substitution andpermutation boxes in each of 16 rounds.

DES could not keep up with advancement in technology

and it is no longer appropriate for security.

By design AES is faster in software and works efficiently inhardware. It works fast even on small devices such as smart

phones, smart cards etc. AES provides more security dueto larger block size and longer keys.



Conclusion: We have studied both AES and DES encryption

algorithms and have highlighted some of the importantmathematical properties as well as the security issues of

both algorithms. Since AES provides better security thanDES and has less implementation complexity, it hasemerged as one of the strongest and most efficientalgorithms in existence today.

Hence, the optimal solution is the use of a hybridencryption system in which typically AES is used to encryptlarge data block.



References: J. D. Johnston, “Testing Loudness Models–Real vs. Artificial Content”, 125 AES

Convention, New York, NY, October 2-5, 2008.

J. D. Johnston and Smirnov, Serge, “A Low Complexity Perceptually TunedRoom Correction System”, 123 AES Convention, New York, NY, October 5-8,

2007. J. D. Johnston, “Perceptual Audio Coding - A History and Timeline”, 41st

Asilomar Conference on Signals, Systems and Computers, 2007.

J. Li, and J. D. Johnston, “Perceptually layered scalable coding”, 40th AsilomarConf. on Signals, Systems and Computers, pp.2125-2129, Pacific Grove, CA,

October 2006.



Thank you



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