17 research outputs found
Linear cryptanalysis of pseudorandom functions
Relatório de projeto de pesquisa.In this paper, we study linear relations propagating across block ciphers from the key input to the ciphertext (for a fixed plaintext block). This is a usual setting of a one-way function, used for instance in modes of operation such as KFB (key feedback). We instantiate the block cipher with the full 16-round DES and -DES, 10-round LOKI91 and 24-round Khufu, for which linear relations with high bias are well known. Other interesting targets include the full 8.5-round IDEA and PES ciphers for which high bias linear relations exist under the assumption of weak keys. Consequences of these findings impact the security of modes of operation such as KFB and of pseudorandom number/bit generators. These analyses were possible due to the linear structure and the poor diffusion of the key schedule algorithms. These findings shall motivate carefull (re)design of current and future key schedule algorithms
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Cryptoraptor : high throughput reconfigurable cryptographic processor for symmetric key encryption and cryptographic hash functions
textIn cryptographic processor design, the selection of functional primitives and connection structures between these primitives are extremely crucial to maximize throughput and flexibility. Hence, detailed analysis on the specifications and requirements of existing crypto-systems plays a crucial role in cryptographic processor design. This thesis provides the most comprehensive literature review that we are aware of on the widest range of existing cryptographic algorithms, their specifications, requirements, and hardware structures. In the light of this analysis, it also describes a high performance, low power, and highly flexible cryptographic processor, Cryptoraptor, that is designed to support both today's and tomorrow's encryption standards. To the best of our knowledge, the proposed cryptographic processor supports the widest range of cryptographic algorithms compared to other solutions in the literature and is the only crypto-specific processor targeting the future standards as well. Unlike previous work, we aim for maximum throughput for all known encryption standards, and to support future standards as well. Our 1GHz design achieves a peak throughput of 128Gbps for AES-128 which is competitive with ASIC designs and has 25X and 160X higher throughput per area than CPU and GPU solutions, respectively.Electrical and Computer Engineerin
An enhanced Blowfish Algorithm based on cylindrical coordinate system and dynamic permutation box
The Blowfish Algorithm (BA) is a symmetric block cipher that uses Feistel network to iterate simple encryption and decryption functions. BA key varies from 32 to 448 bits to ensure a high level of security. However, the substitution box (S-Box) in BA occupies a high percentage of memory and has problems in security, specifically in randomness of output with text and image files that have large strings of identical bytes. Thus, the objective of this research is to enhance the BA to overcome these problems. The research involved three phases, algorithm design, implementation,
and evaluation. In the design phase, a dynamic 3D S-Box, a dynamic permutation box (P-Box), and a Feistal Function (F-Function) were improved. The improvement involved integrating Cylindrical Coordinate System (CCS) and dynamic P-Box. The enhanced BA is known as Ramlan Ashwak Faudziah (RAF) algorithm. The
implementation phase involved performing key expansion, data encryption, and data decryption. The evaluation phase involved measuring the algorithm in terms of memory and security. In terms of memory, the results showed that the RAF occupied 256 bytes, which is less than the BA (4096 bytes). In terms of randomness of text and image files that have large strings of identical bytes, the average rate of randomness for 188 statistical tests obtained values of more than 96%. This means
that the RAF has high randomness indicating that it is more secured. Thus, the results showed that the RAF algorithm that integrates the CCS and dynamic P-Box serves as an effective approach that can consume less memory and strengthen security
KronCrypt - A New Symmetric Cryptosystem Based on Kronecker\u27s Approximation Theorem
In this paper we show how to use an old mathematical concept of diophantine analysis, the approximation theorem of Kronecker, in symmetric cryptography. As a first practical application we propose and analyze the new symmetric 128-bit block cipher KronCrypt. The cipher is a 4-round Feistel network with a non-bijective round function f made up of a variable number of large key-dependent S-boxes, XORs and modular additions. Its key length is variable but not less than 128 bit. The main innovation of KronCrypt in the area of symmetric cryptography is the fact that the key-dependent S-boxes are based upon a constructive proof of the approximation theorem of Kronecker used as a boolean function. We prove the correctness of our concept in general and show how we designe the new cipher KronCrypt. Furthermore, results concerning statistical behaviour, i.e. confusion, diffusion and completeness, and differential cryptanalysis are presented
Differential Cryptanalysis of Feistel’s Iterated Block Ciphers
В статті обговорюються базові принципи Диференційного криптоаналіза, концепції, алгоритми, ідеї і методи, які забезпечують цей тип атаки, а також математичне обгрунтування.Here are described the basic principles of Differential Cryptanalysis, concepts, algorithms, ideas and methods which provide this kind of attack and also its mathematical background
Порівняльний аналіз методів побудови та властивостей S-блоків ряду сучасних криптографічних алгоритмів
Розглянуто методи побудови та властивості збалансованих булевих відображень (S-блоків) нелінійних вузлів ускладнення сучасних криптографічних алгоритмів. Проведено порівняльний аналіз властивостей S-блоків криптографічних алгоритмів Rijndael, Skipjack, Whirlpool, Twofish, Сrypton, Snow, E2, Square, Safer+, Торнадо та інших. Наведено приклад трьох 8x8 S-блоків, в яких координатні функції мають високі показники нелінійності, задовольняють "суворому лавинному критерію" та властивості кореляційної імунності першого порядку.The construction methods and properties of balanced Boolean mappings (S-boxes) to be used in cryptographic transformations of up-to-date cryptographic algorithms are considered.The comparative analysis of properties of S-boxes to be used in Rijndael, Skipjack, Whirpool, Twolish, Crypton, Snow, E2, Square, Safer+, Tornado and others cryptographic algorithms is presented. An example of 8x8 S-boxes, that have high nonlinearity and meet to strict avalanche criterion and correlation immunity of first degree is given
Design Of FPGA-Based Encryption Chipusing Blowfish Algorithm
Nowadays, the world has changed so rapidly that everything has become digitized and computerized. Unfortunately, digital information is very easy to be duplicated, modified,
transmitted or used by unauthorized users. This results a serious problem and in view of this, some sort of security mechanism has to be produced to protect it. This is where the
study of cryptography comes in. Cryptography has been introduced to protect the information. However, until now, the cryptography hardware is still not commonly used especially in FPGA. In this project, the Blowfish encryption algorithm is chosen because it is among the safest algorithm used nowadays. The aim of this project is to design a Blowfish encryption chip in FPGA. For this project, the design entry used is
Altera’s Quartus II Version 5.0 and the targeted hardware is Altera’s Flex10K FPGA device. By using FPGA device, data can be encrypted or decrypted in real time and this would be a great tool for security purpose, such as ATM machine. The first stage of this project is the study of Blowfish algorithm and translates the method into VHDL code because VHDL has been commonly used as a design entry language for FPGA in digital
design. Producing the VHDL code is the most difficult and time-consuming part throughout this project. In the second stage, the design is realized using the FPGA board. In this stage, timing is the most critical factor that must be taken care of. If the timing is incorrect, the output may be wrong. Comparison will be done on the software result and hardware result to ensure that the encryption chip is designed correctly and function well
Two-Key Dependent Permutation for Use in Symmetric Cryptographic System
This paper deals with a two-key based novel approach for generating a permutation table that can be used in a symmetric cryptographic system to cause diffusion. It also discusses how the permutation table generated using the approach can be applied to character based encryption and binary data block produced at intermediate stages by symmetric cipher algorithms. It also describes the effect of our approach on characters of intermediate text as well as on bits of binary data block along with the impact of a single bit change in key information on producing permutation sequences applied to plaintexts to produce ciphertexts. The results are satisfactory and the proposed approach can be employed in any symmetric block cipher algorithm that uses the predefined permutation tables
Dynamic block encryption with self-authenticating key exchange
One of the greatest challenges facing cryptographers is the mechanism used
for key exchange. When secret data is transmitted, the chances are that there
may be an attacker who will try to intercept and decrypt the message. Having
done so, he/she might just gain advantage over the information obtained, or
attempt to tamper with the message, and thus, misguiding the recipient.
Both cases are equally fatal and may cause great harm as a consequence.
In cryptography, there are two commonly used methods of exchanging secret
keys between parties. In the first method, symmetric cryptography, the key is
sent in advance, over some secure channel, which only the intended recipient
can read. The second method of key sharing is by using a public key exchange
method, where each party has a private and public key, a public key is shared
and a private key is kept locally. In both cases, keys are exchanged between
two parties.
In this thesis, we propose a method whereby the risk of exchanging keys
is minimised. The key is embedded in the encrypted text using a process
that we call `chirp coding', and recovered by the recipient using a process
that is based on correlation. The `chirp coding parameters' are exchanged
between users by employing a USB flash memory retained by each user. If the
keys are compromised they are still not usable because an attacker can only
have access to part of the key. Alternatively, the software can be configured
to operate in a one time parameter mode, in this mode, the parameters
are agreed upon in advance. There is no parameter exchange during file
transmission, except, of course, the key embedded in ciphertext.
The thesis also introduces a method of encryption which utilises dynamic blocks, where the block size is different for each block. Prime numbers are
used to drive two random number generators: a Linear Congruential Generator
(LCG) which takes in the seed and initialises the system and a Blum-Blum
Shum (BBS) generator which is used to generate random streams to encrypt
messages, images or video clips for example. In each case, the key created is
text dependent and therefore will change as each message is sent.
The scheme presented in this research is composed of five basic modules. The
first module is the key generation module, where the key to be generated is
message dependent. The second module, encryption module, performs data
encryption. The third module, key exchange module, embeds the key into
the encrypted text. Once this is done, the message is transmitted and the
recipient uses the key extraction module to retrieve the key and finally the
decryption module is executed to decrypt the message and authenticate it.
In addition, the message may be compressed before encryption and decompressed
by the recipient after decryption using standard compression tools