The document discusses the Caesar cipher, highlighting its advantages and disadvantages as a basic encryption method. It also presents a program that performs a letter frequency attack to generate potential plaintexts from ciphertexts, alongside a case study on lightweight cryptography tailored for resource-constrained devices. The conclusion emphasizes the ongoing evolution and potential of lightweight cryptography in securing IoT and embedded systems.

1. CRYPTOGRAPHY

2. C O N T E N T S
2
o Introduction
o Problem Statement
o Case Study
o Conclusion

3. INTRODUCTION

4. 4
o Additive cypher is also known as Caesar Cipher.
o The Caesar cipher is a simple encryption technique that was used by Julius
Caesar to send secret messages to his allies.
o The Caesar Cipher technique is one of the earliest and simplest methods of
encryption technique.

5. ADVANTAGES
• Easy to implement and use thus, making suitable for beginners to learn about
encryption.
• Requires only a small set of pre-shared information.
• Can be modified easily to create a more secure variant, such as by using a
multiple shift values or keywords.

6. DISADVANTAGES
• This is not secure against modern decryption methods.
• The small number of possible keys means that an attacker can easily try all
possible keys until the correct one is found, making it vulnerable to a brute
force attack.
• Does not provide confidentiality, integrity, and authenticity in a message.

7. PROBLEM STATEMENT
a)Write a program that can perform a letter frequency attack on an additive cipher
without human intervention. Your software should produce possible plaintexts in
rough order of likelihood. It would be good if your user interface allowed the user to
specify "give me the top10 possible plaintexts".
b)Give the case study on Lightweight cryptography

8. 8
plaintext = "TheWarisPostpontedto12noon"
key = 5
ciphertext = encrypt(plaintext, key)
print("Ciphertext:", ciphertext)
possible_plaintexts = []
rng=int(input(‘How many plaintext do you require: ’))
for i in range(rng):
possible_plaintext = decrypt(ciphertext, i)
possible_plaintexts.append(possible_plaintext)
print("Possible plaintexts:")
for possible_plaintext in possible_plaintexts:
print(possible_plaintext)

9. 9 PROGRAM
o Encryption:
def encrypt(plaintext, key):
ciphertext = ""
for char in plaintext:
if char.isalpha():
if char.isupper():
ciphertext += chr((ord(char) + key - 65) % 26 + 65)
else:
ciphertext += chr((ord(char) + key - 97) % 26 + 97)
else:
ciphertext += char
return ciphertext

10. 10 o Decryption
def decrypt(ciphertext, key):
plaintext = ""
for char in ciphertext:
if char.isalpha():
if char.isupper():
plaintext += chr((ord(char) - key - 65) % 26 + 65)
else:
plaintext += chr((ord(char) - key - 97) % 26 + 97)
else:
plaintext += char
return plaintext

11. 11 o OUTPUT
Ciphertext: YmjBfwnxUtxyutsyjiyt12stts
Possible plaintexts:
YmjBfwnxUtxyutsyjiyt12stts
XliAevmwTswxtsrxihxs12rssr
WkhZdulvSrvwsrqwhgwr12qrrq
VjgYctkuRquvrqpvgfvq12pqqp
UifXbsjtQptuqpoufeup12oppo
TheWarisPostpontedto12noon
SgdVzqhrOnrsonmsdcsn12mnnm
RfcUypgqNmqrnmlrcbrm12lmml
QebTxofpMlpqmlkqbaql12kllk
PdaSwneoLkoplkjpazpk12jkkj

12. CASE STUDY
Lightweight-Cryptography Status and Future Challenges

13. 13
o The rapid proliferation of resource-constrained devices in the Internet of
Things (IoT), wearable technology, and embedded systems has created a
critical need for lightweight cryptography.
o These devices often lack the processing power, memory, and battery life to
handle traditional cryptographic algorithms. Lightweight cryptography
addresses this challenge by offering efficient and secure solutions
specifically tailored for resource-constrained environments.

14. 14

15. 15 o Some of the best cypher used in lightweight cryptographic systems :
o Block Ciphers:
o PRESENT: Popular for its small code size and fast execution, offering good security against
known attacks. This is a 64-bit block cipher with 80 rounds.
o Speck: Similar to PRESENT, but with an improved resistance against cryptanalysis. This is
a 64-bit block cipher with 32 rounds.
o SKINNY: Highly efficient and secure, particularly suited for resource-constrained devices.
SKINNY offering different bit sizes (64, 128, and 256) and rounds(48, 64 and 96).
o Stream Ciphers:
o Trivium: Widely used with a strong encryption and decryption design and efficient
implementation. Uses 80 bite key size
o Grain: Another strong option with flexible key sizes and good hardware performance. Uses
128 bite key size.
o Hash Functions:
o Keccak (SHA-3): NIST(National Institute of Standards and Technology)-approved secure
hash function with high resistance against collision attacks. Uses SHA3-256(most common)
o Poly1305: Compact and efficient hash function suitable for authentication and integrity
verification. Uses 128 bits key size

16. 16 o Current Status:
o Algorithm advancements: Significant progress has been made in developing efficient
and secure lightweight algorithms for various cryptographic primitives, including block
ciphers , stream ciphers , hash functions.
o Hardware integration: Some manufacturers are integrating dedicated hardware
accelerators for lightweight cryptography into their chips, further boosting performance and
reducing power consumption.
o Software libraries and tools: Open-source libraries and tools are readily available for
developers to implement lightweight cryptography in their projects.

17. 17
o Challenges:
o Security : Balancing security strength with resource efficiency remains a challenge.
While some algorithms offer strong security.
o Vulnerability discovery: New vulnerabilities in existing algorithms are always a
possibility.
o Standardization limitations: Existing standards may not encompass all use cases or
future advancements, requiring continued standardization efforts.
o Lack of awareness: Many developers may not be aware of the benefits of lightweight
cryptography or lack the expertise to implement it effectively.

18. 18
o Future Directions:
o Research on novel algorithms: Exploring new mathematical approaches and
techniques to achieve even greater efficiency and security.
o Hardware-software co-design: Optimizing algorithms for specific hardware platforms to
maximize performance and minimize resource usage.
o Formal verification and analysis: Rigorously verifying the security of lightweight
algorithms to ensure their robustness against attacks.
o Standardization evolution: Adapting and expanding existing standards to keep pace
with technological advancements and emerging use cases.

19. 19
o Conclusion
Lightweight cryptography is a rapidly evolving field with immense potential to
secure the future of resource-constrained devices. Addressing the current
challenges and actively pursuing research and development will ensure that
lightweight cryptography remains a reliable and efficient tool for building
secure and trustworthy systems in various applications.

20. THANK
YOU