MODERAN BLOCK CIPHER

1. HASHMI SAFWAN
MODERN SYMMETRIC BLOCK CIPHER(CRYPTOP)

2. HASHMI SAFWAN
Table of Contents
Moderan Block Cipher.................................................................................................................... 1
1.1 CRYPTON Cipher.....................................................................................................1
1.1.1 Design History.............................................................................................. 1
1.1.2 Mian Features ............................................................................................... 2
1.1.3 High Level Strcuture of CRYPTON ............................................................ 2
1.1.4 Notations.......................................................................................................3
1.1.5 Basic Building Blocks ..................................................................................3
1.1.6 Encryption / Decryption ...............................................................................3
1.1.7 Byte-Wise Subtitution ..................................................................................4
1.1.8 Column Wise Bit Permutation......................................................................4
1.1.9 Column to Row Transpositions....................................................................5
1.1.10 Key Scheduling ..........................................................................................5
1.1.11 Diffusion Property........................................................................................6
1.1.12 Possible Attacks............................................................................................ 6
1.1.13 Conclision.....................................................................................................6
Referebces......................................................................................................................................... 7

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List of Figures
Fig 1.1 High Level Structure of Crypton ............................................................................2
Fig 1.2 Data Representation Array.......................................................................................3
Fig 1.3 Byte-Wise Substitution ...........................................................................................4
Fig 1.4 Byte-Wise Permutation(a) .......................................................................................4
Fig 1.4 Byte-Wise Permutation(b) .......................................................................................5
Fig 1.5 Colum to Row Transposition ..................................................................................5
Fig 1.6 Key Scheduling........................................................................................................5
Fig 1.7 Minimum Diffusion Patterns ..................................................................................6
MODERAN BLOCK CIPHER

4. HASHMI SAFWAN
In cryptography, a block cipher is a deterministic algorithm operational on fixed-length
groups of bits, referred to as blocks, with associate unvarying transformation that's
specified by a symmetric key. Block ciphers operate as necessary elementary
elements within the design of the many cryptological protocols, widely used to
implement encryption of bulk data.
The modern design of block ciphers is predicated on the conception of associate
degree iterated product cipher. In his seminal 1949 publication, communications of
Secrecy Systems, technologist analysed product ciphers and instructed them as a way
of effectively rising security by combining easy operations like substitutions and
permutations.[1] Iterated product ciphers perform encoding in multiple rounds, every of
that uses a distinct sub key derived from the first key. One widespread implementation
of such ciphers, named a Feistel network once crust Feistel, is notably implemented
within the DES cipher [2]. several alternative realizations of block ciphers, like the AES,
are classified as substitution-permutation networks [3].
1.1 Crypton Cipher
The block cipher Crypton is design base on the latter approach. Each block is
representing it into 4 x 4 byte arrays. The round transformation of Crypton
consists of 4 parallelizable step.
1. Byte-Wise substitution.
2. Column wise bit permutation
3. Column to row transposition and
so
4. key additions.
The decryption process can be
created identical as encryptions
method except that sub keys are
applied on every round.
1.1.1 Design History
Main Objective of this cipher are,
• An efficient and Secure block cipher
• Security: high enough to defeat numerous existing attacks like
differential and linear cryptanalysis.
• Simplicity
• Efficiency:
o high performance in code on giant microprocessors
o efficient implementation on cheap 8-bit microprocessors

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o very high speed in hardware low hardware quality
• Design Choices
o Substitution Permutation Network (SPN)
SPN more parallelism then Feistel, More hardware-efficient and
more constraint in round function design.
1.1.2 Main Features
• Secure against existing attacks
• A simple, fine-grained design: straightforward to implement/analyze
• Symmetry in encryption and decryption
• High performance on most hardware architectures
• Fast key scheduling: a lot of quicker than one-block encryption
efficient hardware implementation and low complexity.
• High degree of similarity, terribly high speed in hardware: are able
to do many Gbits/sec exploitation concerning 30000 gates
1.1.3 High Level Structure of Crypton
Fig. 1.1 High Level Structure of Crypton
1.1.4 Notation

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Data representation in 4 x 4-byte array.
Fig 1.2 Data Representation Array
1.1.5 Basic Building Blocks
• Components of Round Transformation
o Byte-wise Substitution 
o Column-wise Bit Permutation 
o Column-to-Row Transposition 
o Key Xoring 
• Round Transformation 
o Even round rounds: eK = K o  o e o e
o Odd rounds: oK = K o  o o o o
1.1.6 Encryption/Description
• Round keys
o i-th round encryption: Ke
i = {Ke [4i+j]}(0  j  3)
o i-th round decryption: Kd
i = {Kd [4i+j]}(0  j  3)
o e =  o e o , o =  o o o 
o Kd
i = e(Ke
i) for even i, o(Ke
i) for odd i.
• Encryption EK
0121112
eeeee KeKeKeKeKe   
• Decryption DK
Same as encryption except for using Kd instead of Ke.
1.1.7 Byte wise Substitution 

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Fig 1.3 Byte-Wise Substitution
1.1.8 Column-wise Bit Permutation  (1)
Fig 1.3 Byte-Wise Permutation (a)

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Fig 1.4 Byte-Wise Permutation (b)
1.1.9 Column-to-Row Transposition  / Key Add 
Fig 1.5 Colum to Row Transposition
1.1.10 Key Scheduling
Two step key generation
Fig 1.6 Key Scheduling

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1.1.11 Diffusion Property of (1)
Active diffusion order 4/(at least 4 active bytes on average per round)
Fig 1.7 Minimum Diffusion Patterns by  o 
1.1.12 Possible Attacks
• interpolation attacks: no simple algebraic description
• Dedicated SQUARE attacks:
a. the best known attack up to 6 rounds
b. can’t be extended to more round versions
• Side-channel cryptanalysis:
c. timing attacks
d. differential fault analysis
e. differential power analysis
f. Key schedule cryptanalysis
g. weak keys, semi-weak keys, equivalent keys
h. simple relations, related keys
1.1.13 Conclusions
• Advantages:
o strong security against various known attacks (with at least 3-round
safety margin)
o symmetry in encryption and decryption
o uniformly fast on various architectures in software
o efficiently implementable in hardware
o high degree of parallelism: very high speed in hardware
• Remarks:
Can be freely used: royalty-free

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References:
1. Shannon, Claude (1949). "Communication Theory of Secrecy Systems".
Bell System Technical Journal. 28 (4): 656–715.
2. Jump up ^ van Tilborg, Henk C. A.; Jajodia, Sushil, eds. (2011).
Encyclopedia of Cryptography and Security. Springer. ISBN 978-1-4419-
5905-8., p. 455.
3. Jump up ^ van Tilborg & Jajodia 2011, p. 1268.
4. Chae Hoon Lim, CRYPTON: A New 128-bit Block Cipher p.1-30