LALE: Yeni bir hafif siklet blok şifreleme algoritması tasarımı
LALE: A new lightweight block encryption algorithm design
Yazar: FATMA BETÜL PAK
Danışman: PROF. DR. MEHMET ÖZEN
Sakarya Üniversitesi / Fen Bilimleri Enstitüsü / Matematik Ana Bilim Dalı / Cebir ve Sayılar Teorisi Bilim Dalı
Derece: Yüksek Lisans, 2023
Konu: Bilim ve Teknoloji = Science and Technology ; Matematik = Mathematics
Dizin: Kriptoloji = Cryptology ; Şifreleme = Encryption ; Şifreleme sistemleri = Encryption systems

Özet:
Teknolojide son dönemde yaşanan büyük gelişmeler ile veri güvenliğini sağlamak 
önemli bir sorun haline gelmiştir. Tarihi çok eskiye dayanan Kriptoloji bilimi, 
insanların güvenli bir şekilde haberleşmesi, veri aktarması ya da verileri depolaması 
için ortaya çıkmış bir bilim dalıdır. Geliştirilen şifre sistemlerin en temel amacı 
gizliliği önem arz eden verileri saklamak ya da iletmektir. Bugüne kadar veri 
güvenliğini sağlamak için birçok tarihi ve modern şifre sistemleri tasarlanmıştır. 
Geleneksel şifreleme algoritması olarak bilinen bu şifreleme sistemleri kaynak 
yönünden zengin cihazlarda, büyük verilerin şifrelenmesinde kullanılır. Ancak bu 
algoritmalar IOT gibi kaynak yönünden kısıtlı cihazlar için enerji tüketimi anlamında 
kullanıma uygun değildir. Bu durumda Hafif kriptografi etkili bir çözümdür. 
Hafif kriptografi algoritmaları, kaynak kısıtlı cihazlarda ihtiyaç duyulan performans 
ve güvenliği sağlayan şifreleme sistemleridir. Bugüne kadar geliştirilmiş Hafif 
kriptografi sistemleri incelendiğinde, sistemlerde farklı tasarım yöntemleri tercih 
edildiği, bu sebeple birbirinden farklı performans ve güvenlik özelliklerine sahip 
sistemler elde edildiği gözlemlenmiştir. Genel olarak bir şifreleme sisteminin 
tasarımında, bu sistemlerin en önemli kullanım sebebi olan güvenlik ön planda 
tutulmaya çalışılır. Ancak Hafif kriptografi şifreleme sistemlerinin daha çok küçük 
cihazlar için geliştirilmesi ve bu cihazların kaynak yönünden kısıtlı olmaları nedeniyle 
böyle cihazlarda güvenliği sağlamanın yanında hızlı olması ve enerji tüketiminin en 
az seviyede olmasını sağlamak gerekmektedir. Bugüne kadar geliştirilen Hafif şifre 
sistemleri de bu amaçla tasarlanmıştır. Ancak yapılan performans ve güvenlik 
ölçümleri karşılaştırması sonuçlarına göre sistemlerin yeterli güvenlik seviyesini 
sağlarken performans açısından iyi olmadığı ya da performans açısından iyi durumda 
iken güvenlik yönünden zayıf olduğu ortaya çıkmaktadır. 
Bu tez çalışmasının amacı, Nesnelerin İnterneti (IOT) gibi kaynak kısıtlı cihazlarda 
güvenliği sağlayan, performans açısından iyi olan yeni bir Hafif şifre sistemi 
tasarlamak ve ölçümlerini yapmaktır. Bilinen en güçlü analitik saldırı çeşitlerinden biri 
olan diferansiyel kriptanaliz, İntegral saldırısı ve Kendine benzerlik saldırısı yapılarak 
LALE'nin güvenlik ölçümleri yapılmıştır. Yeni şifre sistemi, bu saldırılara karşı 
oldukça güvenlidir. Sistemin güvenliğinde önemli rolü olan S-box katmanının tasarımı 
için DNA şifreleme tabanlı yepyeni bir yöntem geliştirilmiştir ve bu yöntem ile yeni 
bir 4x4 S-box tasarlanmıştır. Yeni Hafif şifre sistemi tasarımımızın yazılım 
uygulaması yapılarak şifreleme ve deşifreleme süreleri ve RAM ölçümleri 
yapılmışıtır. Buna göre LALE, AES gibi bilindik diğer şifre sistemlerine göre daha 
hızlıdır.

Abstract:
The Internet of Things (IoT) is one of the most important technology which will 
interact the human world with the every machine. IOT is used in transport, logistics, 
environment, infrastracture which are smart (such as smart cities, smart malls, smart 
homes and industry 4.0), smart healthcare and agriculture, RFID tags, sensor nodes, 
battery operated portable devices and medical implants and many more. The definition 
of IOT can be expressed as a network of connected devices, which have their own 
unique identification. It can collect and interchange data through the network whether 
any human interference or not.
When billions of connected devices are working together, particularly when 
transferring the data from server to sensors, it leads to many kinds of problems to users 
such as interoperability, privacy, longevity, and much more. As IOT devices are easily 
available and interact with the material world to accumulate private data, that makes 
them an tempting target to attackers and exposed to various security attacks. Hence 
cybersecurity gain prominence in IOT.
With the recent big developments in technology, ensuring data security has become an 
important issue. Cryptology, which dates back a long time, is a branch of science that 
has emerged for people to communicate, transfer data or store data securely. 
Cryptography is a great solution to enhance the security of the stored data over the 
internet. However, conventional cryptography algorithms which are appropriate for 
PCs and have high resource requirement can't be adopted for IOT devices which are 
resource-constrained. With the introduction of AES, it become an remarkable and 
preferred option for some applications of block ciphers. As resource-constrained IOT 
devices have power, size and memory constraints, AES is often inproper for them. In 
these circumstances Lightweight Cryptography is an effective solution. Lightweight 
Cryptography algorithms are encryption systems that provide the performance and 
security trade-off which is needed in resource-constrained devices. Hence, in the last 
years many researches have been conducted based on lightweight ciphers by 
researchers. Especially on designing lightweight blockciphers with particularly low 
implementation costs and analyzing them has drawn significant attention. 
Lightweight cryptography algorithms have the following three foundamental 
properties. When cryptography is applied to any IOT device which is resource 
constrained, performance, cost and security are the main properties. By using simple 
round functions on the small block using a small key with simple key scheduling, LWC 
algorithms satisfy the performance and cost properties. With the adoption of one of 
the six internal structures (SPN, FN, Hybrid, GFN, NLFSR, ARX) LWC algorithms satisfy the last and important property which is security, to resist against the security 
attacks. While constructing the round function, the size of its components, S-box, how 
and at what stage the round constant addition will be, the type of permutation, or the 
type of the key sheme, size of the key and the block, and of course the internal structure 
part, etc. different choices in algorithms induce different properties. These properties 
leads to various consequences in algorithms. 
When compared the lightweight algorithms in terms of performance,some results were 
obtained. Speck and Simon algorithms are the best when compared with other 
lightweight algorithms in terms of software efficiency. At memory requirements, 
Simon and Speck are again leading with 200 bytes of ROM and 0 bytes of RAM. In 
terms of Hardware efficiency, Midori and Piccolo are the leading ones. SEA and 
Hummingbird algorithms are the best when compared the effect of block and key 
length in hardware. When compared in terms of Physical area requirement, Ktantan 
requires only 462 GE, and Print cipher comes in second place with 503 GE. Moreover 
in terms of energy comsumption, Midori, Piccolo and Prince are respectively the best, 
with small differences. When we look at the comparisons in terms of performance, it 
is obvious that there is no algorithm that is good in every field. For example Simon 
has good results in software efficiency and memory requirements but it is not good in 
terms of energy cunsumption. When compared in terms of security, all algorithms are 
vulnerable to various attacks. Hence the choices made during the design phase cause 
different results.
The aim of this these is presenting a new lightweight block cipher which is easily 
adoptable in resource constrained devices. Before making our new design, many 
lightweight algorithms in the literature were examined. There are many lightweight 
cryptography algorithms on the market. However most algorithms are unable to 
achieve the balance between the energy consumption and security. When these 
algorithms were examined, we observed that the differences of the components used 
in their content, make algorithms advantageous in certain aspects, while 
disadvantaging them in many other fields. Considering these reviews, a brand new 
algorithm has been obtained that balances safety, energy and cost, each component of 
which has been designed carefully.
Components of the new proposed cipher, such as Substitution layer, Key Scheduling, 
Permutation layer, etc. was designed with security and energy balance in mind. The 
new cipher's 4x4 S-box is designed in a brand new way which is based on DNA 
encryption. We have used a key whitening process to increase its resistance against 
cryptanalytic attacks. Round constant addition part has also been carefully chosen to 
maintain the balance of energy and cost. The structure of the new introduced cipher is
hybrid structured which is obtained by combining SPN and Feistel Network. An 
algorithm with optimum value was obtained by using the unique features of SPN and 
Feistel structure together. 
Our new introduced cipher provides 64-bit block in order to make it suitable for 
standard applications and 128-bit key to achieve the required security level. The 
structure of the cipher is in Hybrid type which combines the SPN and the Feistel 
Network. The structure of other lightweight algorithms is generally preferred as SPN 
or Feistel Network. However, these two structures have their own advantages and 
disadvantages. Substitution Permutation Network and Feistel Network are the famous 
structures of block ciphers thanks to their adaptability to application necessity. Round 
function is applied to only one half of the block in Feistel structures and they can be 
implemented with low power in hardware. As Feistel type structures introduce such a 
nonlinearly round function, such constructions usually require more enforcement of
round functions to sustain the security level as compared to SPN structures. For this 
reason, the structure of the cipher was preferred as a hybrid structure where we can 
use the features of SPN and Feistel Network.
In the light of those informations we have used a new approach at designing the new 
cipher. SPN and Feistel Network is combined with low number of rounds which 
enables us to achieve high security level. The decryption and encryption function of 
the new introduced cipher is quite similar. Hence LALE has roughly the same physical 
requirements to implement encryption and decryption.
LALE's round number is 10-2 which achieves the high security level. 10-2 round 
means that the round number of SPN part is 10, and number of rounds of the Feistel 
part is 2. Accordingly, it is necessary to apply the 10-2 round version of the cipher for 
security purposes to devices that are resource-limited, such as IoT. If desired, in other 
large devices or systems, a structure with the round of 12-2 or 16-2 should be applied 
for advanced safety purposes. Likewise if desired, in other IOT devices for low energy 
usage and speed, a structure with round of 8-2 should be applied. 
Various attacks have been applied to measure the security of the new encryption 
system, which is 10-2 round. According to the result of the differential attack, the new 
10-round encryption system provides a sufficient level of security. It seems that the 
factors that increase the system's resistance to integral attack and self-similarity attacks 
are found in the new healing system, so it is safe against these attacks. We make the 
performance measurement of the new cipher by making its software implementation
with C++. We measure the encryption and decryption times of our new introduced 
cipher LALE. The results of our new introduced cryptography algorithm LALE is
given in a table. At the same time, we have compared LALE with other cryptographic 
systems in terms of encryption and decryption times. According to the results 
obtained, the new introduced system is faster than some other algorithms like AES, 
Lblock, Present and Piccolo. We also did the RAM measurement and give it in a table.