09-07-2012, 03:40 PM
Enhancement of Security through an Efficient Substitutionbased
Block Cipher of Bit-level Implementation with Possible
Lossless Compression
[attachment=27290]
Introduction
Cryptography is an essential tool of data security
through mathematical manipulation of data with an
incomprehensible format for unauthorized person.
Lossless data compression ensures storage efficiency.
Incorporation of size-reduction while implementing a
ciphering protocol introduces a special dimension in the
scope of encryption.
In this paper, a substitution-based, private-key,
block cipher, termed as “Block Substitution with the
Sequential Position of Sorted Distinct blocks on
Frequency (BSSPSDF)” is presented, which is modeled
for implementing at bit-level with decomposing equal
block length. This storage-efficient, cipher BSSPSDF is
generated smaller encrypted bit-stream in size than the
source one, but it depends on context of the plain text.
The scheme for deciphering technique
After receiving the target block and key, receiver
comes to know information for each block, which was
sending. After receiving the required information, the
decryption authority performs the task of decryption.
From key, receiver comes to know source block
length, say L, unchanged block length, say NUB, number
of dummy 0, say D0 and number of distinct blocks,
appeared in source bit stream, say N and obviously total
set of distinct blocks in source bit stream with their
sequence.
The scheme for ciphering technique
At first, source file is convert into binary form i.e.
source bit stream which is decomposed into blocks of
equal length; say L bits where L is an integer and L ≥ 2. It
may be happened that after decomposition of total sourcebit-
stream into some L bits blocks, a blocks, less than L
bits is left at last, say UB (=> length of UB < L) which is
totally unchanged during encryption.
Key generation
For correct decryption for cipher text, correct
Key is essential. For this algorithm key contents 5
segments. 1st segment denotes length of the blocks, while
2nd segment contents number of distinct blocks appeared
in source bits stream. 3rd segment holds number of
unchanged bits during encryption. How many dummy bits
(i.e. 0) are been added to make length of encrypted bit
stream as multiple of 8, is kept in 4th segment and last
segment, means 5th segment holds set of all distinct
International Data Encryption Algorithm (IDEA)
International Data Encryption Algorithm is a
128-bit private key cipher, which is implemented in bit
level with equally decomposed 64 bit blocks of plain text
depending on modular arithmetic. There are regenerated
16-bit 52 sub keys from 128 bits key based on rotational
replacement and some particular rules, say k1, k2, k3 … k52.
A 64-bit block of plain text is decomposed into 4 16-bit
sub blocks; say P1, P2, P3 and P4.
Graphical Test for Frequency Distribution :
We check the degree of security of the proposed
protocol against the cryptanalytic attack using frequency
distribution, where the frequency of the all 256 characters
in source file and their corresponding encrypted file are
compared graphically and we want to observe whether the
exists any fixed relation ship between of the a character in
both source and encrypted file.
Block Cipher of Bit-level Implementation with Possible
Lossless Compression
[attachment=27290]
Introduction
Cryptography is an essential tool of data security
through mathematical manipulation of data with an
incomprehensible format for unauthorized person.
Lossless data compression ensures storage efficiency.
Incorporation of size-reduction while implementing a
ciphering protocol introduces a special dimension in the
scope of encryption.
In this paper, a substitution-based, private-key,
block cipher, termed as “Block Substitution with the
Sequential Position of Sorted Distinct blocks on
Frequency (BSSPSDF)” is presented, which is modeled
for implementing at bit-level with decomposing equal
block length. This storage-efficient, cipher BSSPSDF is
generated smaller encrypted bit-stream in size than the
source one, but it depends on context of the plain text.
The scheme for deciphering technique
After receiving the target block and key, receiver
comes to know information for each block, which was
sending. After receiving the required information, the
decryption authority performs the task of decryption.
From key, receiver comes to know source block
length, say L, unchanged block length, say NUB, number
of dummy 0, say D0 and number of distinct blocks,
appeared in source bit stream, say N and obviously total
set of distinct blocks in source bit stream with their
sequence.
The scheme for ciphering technique
At first, source file is convert into binary form i.e.
source bit stream which is decomposed into blocks of
equal length; say L bits where L is an integer and L ≥ 2. It
may be happened that after decomposition of total sourcebit-
stream into some L bits blocks, a blocks, less than L
bits is left at last, say UB (=> length of UB < L) which is
totally unchanged during encryption.
Key generation
For correct decryption for cipher text, correct
Key is essential. For this algorithm key contents 5
segments. 1st segment denotes length of the blocks, while
2nd segment contents number of distinct blocks appeared
in source bits stream. 3rd segment holds number of
unchanged bits during encryption. How many dummy bits
(i.e. 0) are been added to make length of encrypted bit
stream as multiple of 8, is kept in 4th segment and last
segment, means 5th segment holds set of all distinct
International Data Encryption Algorithm (IDEA)
International Data Encryption Algorithm is a
128-bit private key cipher, which is implemented in bit
level with equally decomposed 64 bit blocks of plain text
depending on modular arithmetic. There are regenerated
16-bit 52 sub keys from 128 bits key based on rotational
replacement and some particular rules, say k1, k2, k3 … k52.
A 64-bit block of plain text is decomposed into 4 16-bit
sub blocks; say P1, P2, P3 and P4.
Graphical Test for Frequency Distribution :
We check the degree of security of the proposed
protocol against the cryptanalytic attack using frequency
distribution, where the frequency of the all 256 characters
in source file and their corresponding encrypted file are
compared graphically and we want to observe whether the
exists any fixed relation ship between of the a character in
both source and encrypted file.