Implemented block ciphers like AES and DES on raw data, using C#, successfully for both encrypting and decrypting raw data.

1. UNDER THE GUIDANCE OF: SUBMITTED BY:
MR. SP MISHRA NAYANIKA DUTT
SCIENTIST F ROLL NO: 53044
SAG, DRDO ECE -VIII SEMESTER
MINISTRY OF DEFENCE KIIT COLLEGE OF METCALFE
HOUSE, ENGINEERING
DELHI-54.
ADVANCED ENCRYPTION
STANDARD

2. ABOUT DRDO
● Defence Research and Development Organisation(DRDO) was formed in 1958
from the amalgamation of the then already functioning Technical Development
Establishment (TDEs) of the Indian Army and the Directorate of Technical
Development & Production (DTDP) with the Defence Science Organisation
(DSO).
● DRDO is a network of more than 50 laboratories which are engaged in
developing defence technologies covering various disciplines, like aeronautics,
armaments, electronics, combat vehicles, engineering systems,
instrumentation, missiles, advanced computing and simulation, special
materials, naval systems, life sciences, training, information systems and
agriculture.
● Presently, the Organisation is backed by over 5000 scientists and about 25,000
other scientific, technical and supporting personnel.
● Several major projects for the development of missiles, armaments, light
combat aircrafts, radars, electronic warfare systems etc are on hand and
significant achievements have already been made in several such technologies.

3. ABOUT SAG
● Scientific Analysis Group (SAG) was established in 1963 for evolving new
scientific methods for design and analysis of communication systems.
● In 1976, SAG started undertaking R&D projects on mathematical,
communication and speech analysis.
● SAG was further entrusted with R&D work in the field of electronics. Work
related to evaluating communication equipment to be introduced in Services
was taken up during 1980.
● Areas of Work: Advanced Mathematical and Statistical Analysis &
Development of Tools Linguistics - Computational and Structural Speech
Analysis - Recognition and Synthesis Simulation Studies Microprocessor-
based Systems Signal Processing Satellite Communication High Performance
Computing

4. BASICS ABOUT SMARTCARDS
● Smart cards are plastic cards containing an embedded microprocessor that
are used as secure devices in a wide range of applications.
● Metal circle - not the microprocessor rather a unit containing its outside
connections.
● Advantages:
● A memory for greater storage than can be provided on magnetic stripes.
● Intelligence for exploiting this increased data. The smart card participates
directly in controlling transactions; i.e. it is active not passive like the
magnetic card
● It cannot be reproduced, nor can its code be broken. After three wrong
codes have been tried, the chip blocks any further usage of the card, which
is therefore more secure than a magnetic card
● It stores formula within its permanent (read-only) memory which enables it
to
● verify the authenticity of the secret code typed in by the customer
● It registers and memorises the number and frequency of all transactions
effected.

5. APPLICATIONS
● Majority of financial orgs have mandated that credit and debit
cards will be smart card enabled.
● Enterprises provide their employees with smart ID badges.
Many governments are issuing smart card-based identity
credentials to their citizens.
● Smart health cards provide security and privacy to patient
information. Medical records are portable for emergency
purposes.
● Latest apps are in the area of transportation: modern parking
systems and public transports like metros(DMRC).
● Students can use their smart card-based IDs for multi
purposes using multi-app OS like MULTOS.
● Cryptography, hence, is used for email encryption, secure web
sites, code breaking(World Warr II) and smart cards.

6. CRYPTOGRAPHY
● Smart cards are used for various types of apps which include storage
and exchange of data. In most cases, this data is confidential, which
if leaked put people’s credentials at stake. Hence the data is
encrypted using certain algorithms called cryptographic algorithm.
● Ex. AES, RSA, DES, Triple-DES etc.
● Sensitive systems that are based on smart cards use protocols and
algorithms that have usually been subjected to rigorous analysis by
the cryptographic community.
● Similarly govt org need to decrypt similar encrypted data collected
from sources which are of national importance. There are such orgs
all around the world. Ex. NSA(US).
● An attacker always looks for the weakest link in your cryptosysytem.
That means we have to choose strong algos.
● Good ciphers should hide the statistical properties of the encrypted
pt. The ct symbols should appear to be normal.

7. ADVANCED ENCRYPTION STANDARD(AES)
● In 1997 NIST called for proposals for a new Advanced Encryption
Standard(AES).
● On October 2, 2000, NIST announced that it had chosen
Rijndael(Dr. Daemen and Dr. Rijmen) as the AES.
● Among the commercial standards that include AES are the Internet
phone Skype and numerous security products around the world. To
date, there are no attacks better than brute-force known against
AES.
● It’s a symmetric block cipher with block size of 128 bit and choice of
three key sizes: 128, 192 and 256 bit.
● The no of rounds through which a text has to go for
encryption/decryption is a function of the key size.
● Separate algorithm is required to derive separate keys(subkey) from
the original key called key schedule.
● The input is arranged into a state matrix and all the operations are
carried on byte level.

8. GALOIS FIELDS(GF)
● Galois Field(GF): A finite field, sometimes also called Galois field, is a set with a finite
number of elements.
● A group is a set of elements G together with an operation ◦ which combines two
elements of G. A group has the following properties:
1. The group operation ◦ is closed. That is, for all a,b,∈G, it holds that a ◦ b = c ∈ G.
2. The group operation is associative. That is, a◦(b◦c)=(a◦b)◦c for all a,b,c ∈ G.
3. There is an element 1∈G, called the neutral element (or identity element), such that a ◦ 1
= 1 ◦ a = a for all a ∈ G.
4. For each a ∈ G there exists an element a−1 ∈ G, called the inverse of a, such that a ◦
a−1 = a−1 ◦ a = 1.
5. A group G is abelian (or commutative) if, furthermore, a ◦ b =b ◦ a for all a,b ∈ G.
● A field F is a set of elements with the following properties:
1. All elements of F form an additive group with the group operation “+” and the neutral
element 0.
2. All elements of F except 0 form a multiplicative group with the group operation “×” and
the neutral element 1.
3. When the two group operations are mixed, the distributivity law holds, i.e., for all a,b,c
∈ F: a(b+c)= (ab)+(ac).

9. LAYERS OF THE ENCRYPTION
● There are 3 types of layers really, although iterations of 1 kind. These
layers comprise of few steps:
● Key Addition layer: A 128-bit round key, or subkey, which has
been derived from the main key in the key schedule, is XORed to the
state.
● Byte Substitution layer (S-Box): Each element of the state is
nonlinearly transformed using lookup tables with special
mathematical properties.
● ShiftRows layer: The ShiftRows transformation cyclically shifts
the second row of the state matrix by three bytes to the right, the
third row by two bytes to the right and the fourth row by one byte to
the right. The first row is not changed by the ShiftRows
transformation.
● MixColumn layer: The MixColumn step is a linear transformation
which mixes each column of the state matrix.

10. KEY SCHEDULE
● The AES key schedule is word-oriented, where 1 word = 32 bits.
Subkeys are stored in a key expansion array W that consists of
words. There are different key schedules for the three different AES
key sizes of 128, 192 and 256 bit.
● For a 128-b key there are 11 subkeys which are stored in a word
matrix containing 44 words. Each row contains 4 words and thus is
a subkey/roundkey.
● First row is the same as the original key. For the remaining rows,
every fifth word is derived as follows
W[4i] =W[4(i−1)]+g(W[4i−1])
where the function g() rotates its four input bytes, performs a byte-
wise S-Box substitution, and adds a round coefficient RC to it.
● The remaining three words of a subkey are computed recursively as:
W[4i+ j] =W[4i+ j−1]+W[4(i−1)+ j]

11. LAYERS OF THE DECRYPTION
● All layers are inverted, i.e., the Byte Substitution layer
becomes the Inv Byte Substitution layer, the ShiftRows layer
becomes the Inv ShiftRows layer, and the MixColumn layer
becomes InvMixColumn layer.
● The order of the subkeys is reversed and there is a change in
the order of the layers in the rounds of decryption.
● Since the XOR operation is its own inverse, the key addition
layer in the decryption mode is the same as in the encryption
mode.
● Inverse MixColumn Sublayer:
● Inverse ShiftRows Sublayer: Shift the rows of the state
matrix in the opposite direction.
● Inverse Byte Substitution Layer: is used when decrypting
a ciphertext.

12. REVERSE KEY SCHEDULE
● There is no requirement of a reverse key schedule if
the key schedule subkeys/roundkeys are only used,
but in a reverse fashion.
● Thus no separate reverse key schedule is required.

14. TEST VECTORS
● Encryption(128-b key):
o Key: 2b7e151628aed2a6abf7158809cf4f3c
o Plaintext: 3243f6a8885a308d313198a2e0370734
o Ciphertext: 3925841d02dc09fbdc118597196a0b32
● Decryption(128-b key):
o Key: 2b7e151628aed2a6abf7158809cf4f3c
o Ciphertext: 3925841d02dc09fbdc118597196a0b32
o Plaintext: 3243f6a8885a308d313198a2e0370734

15. DATA ENCRYPTION STANDARD (DES)
● In 1977 NIST adopted DES as the standard algorithm for
encryption (FIPS PUB 46). Subsequent attacks on DES led
NSA to adapt to Triple DES or 3-DES which was more secure
than DES and only brute force attack was possible on it.
● DES has a block length of 64 bits and a key length of 56 bits
and it’s a block cipher.
● Most encryption algorithms including DES, are based on
Feistel block cipher [FEIS73].
● Majority of network based symmetric cryptographic
algorithms use block cipher.
● A separate key schedule algorithm is required to derive the
subkeys for each of the 16 rounds.
● All the operations occur on bit level.

16. DES ENCRYPTION
● Algorithm contains two parts: one containing the 16
round functions and the key schedule.
● Apart from round function, initial permutation & inverse
initial permutation are other functions through which
the data block goes.
● Key schedule consists of similar 16 rounds of left circular
shift & permuted choice 2 functions. Apart from them
permuted choice 1 is also used.
● In round, right half of data goes through Feistel function
which expands, substitutes & permutes the input data.
● There are 8 S-boxes & each of them have 6-bit input and
4-bit output.

17. DES DECRYPTION
● Decryption algorithm is same as that of encryption.
● The key schedule also being same saves the need for
a different software for it.
● The only difference between encryption and
decryption is that the order of subkeys used is
reversed, i.e. for round 1 subkey 16 is used & for
round 16 subkey 1 is used.

19. TEST VECTORS
● Encryption (64-bit block):
o Key: 10316E028C8F3B4A
o Plaintext: 0000000000000000
o Ciphertext: 82DCBAFBDEAB6602
o Decryption (64-bit block):
o Key: 10316E028C8F3B4A
o Plaintext: 82DCBAFBDEAB6602
o Ciphertext: 0000000000000000

20. Thank You