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Attacking Turkish Texts Encrypted by Homophonic Cipher
ATTACKING TURKISH TEXTS ENCRYPTED BY HOMOPHONIC CIPHER (HOMOFONĠK ġĠFRELENMĠġ TÜRKÇE METĠNLER ÜZERĠNE ATAKLAR) by Şefik İlkin SERENGİL, B.S. Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE in COMPUTER ENGINEERING in the INSTITUTE OF SCIENCE AND ENGINEERING of GALATASARAY UNIVERSITY June 2011 ATTACKING TURKISH TEXTS ENCRYPTED BY HOMOPHONIC CIPHER (HOMOFONĠK ġĠFRELENMĠġ TÜRKÇE METĠNLER ÜZERĠNE ATAKLAR) by Şefik İlkin SERENGİL, B.S. Thesis Submitted in Partial Fulfillment of the Requirements for the Degree of MASTER OF SCIENCE Date of Submission : May 18, 2011 Date of Defense Examination: June 17, 2011 Supervisor : Asst. Prof. Dr. Murat AKIN Committee Members : Assoc. Prof. Dr. Tankut ACARMAN Assoc. Prof. Dr. Y. Esra ALBAYRAK Acknowledgements I would like to thank with my whole heart to my supervisor, Asst. Prof. Dr. Murat Akın, who taught me a lot of things in my academic life. I am grateful to my beloved mother and father who do not avoid sacrificing anything from the day I was born to ensure me to have the best conditions. May, 2011 ġefik Ġlkin Serengil ii Table of Contents Acknowledgements ........................................................................................................... ii Table of Contents ............................................................................................................. iii List of Figures ................................................................................................................... v List of Tables .................................................................................................................. -
Substitution Cipher in Cryptography, a Substitution Cipher Is a Method Of
Substitution cipher In cryptography, a substitution cipher is a method of encryption by which units of plaintext are replaced with ciphertext according to a regular system; the "units" may be single letters (the most common), pairs of letters, triplets of letters, mixtures of the above, and so forth. The receiver deciphers the text by performing an inverse substitution. Substitution ciphers can be compared with transposition ciphers. In a transposition cipher, the units of the plaintext are rearranged in a different and usually quite complex order, but the units themselves are left unchanged. By contrast, in a substitution cipher, the units of the plaintext are retained in the same sequence in the ciphertext, but the units themselves are altered. There are a number of different types of substitution cipher. If the cipher operates on single letters, it is termed a simple substitution cipher; a cipher that operates on larger groups of letters is termed polygraphic. A monoalphabetic cipher uses fixed substitution over the entire message, whereas a polyalphabetic cipher uses a number of substitutions at different times in the message, where a unit from the plaintext is mapped to one of several possibilities in the ciphertext and vice-versa. Contents • 1 Simple substitution o 1.1 Examples o 1.2 Security for simple substitution ciphers • 2 Homophonic substitution • 3 Polyalphabetic substitution • 4 Polygraphic substitution • 5 Mechanical substitution ciphers • 6 The one-time pad • 7 Substitution in modern cryptography • 8 Substitution ciphers in popular culture Simple substitution 1 ROT13 is a Caesar cipher, a type of substitution cipher. In ROT13, the alphabet is rotated 13 steps. -
Chapter 2: Classical Encryption Techniques Cryptography and Information Security
Chapter 2: Classical Encryption Techniques Presented by: Abir EL. 03/16/2021 Professor. 박종혁 Cryptography and information Security 1 Table of Content: • Introduction to encryption • Basic Terminology and key words • Symmetric Cipher Model . Caesar Cipher. Monoalphabetic Cipher. Polyalphabetic Cipher. Playfair Cipher. One-Time Pad. Hill Cipher. • Transposition Cipher . Book Cipher or Running Key Cipher • Product Cipher 2 Classical Encryption Techniques What is Encryption? Encryption, is the process of changing information in such a way as to make it unreadable by anyone except those possessing special knowledge (usually referred to as a "key") that allows them to change the information back to its original, readable form. Goals of this chapter: • Introduce basic concepts and classical terminologies and encryption technologies. • An introduction to the upcoming chapters. 3 Classical Encryption Techniques Basic Terminology and Key words: . Plaintext: Refers to the original text or message to be encrypted. Ciphertext: The encrypted message. Enciphering or Encryption: The process of converting plaintext into a ciphertext. Deciphering or Decryption: The process of decoding the ciphertext and retrieving the original plain text. Encryption algorithms: a pseudocode based on mathematical equations to perform encryption. Usually requires two inputs; the Plaintext and the Secret Key. Decryption algorithm: Used to perform the decryption. Usually requires two inputs as well; Ciphertext and Secret Key. Secret Key: A special key used for encryption and decryption, known as well as Symmetric Key. 4 Classical Encryption Techniques Basic Terminology and Key words: . Cipher or Cryptographic system: Refers to the scheme used for encryption and decryption. Cryptography: The science that studies and analyze ciphers. Cryptanalysis: Science of studying attacks against cryptographic systems. -
On the Construction and Cryptanalysis of Multi-Ciphers
On the Construction and Cryptanalysis of Multi-Ciphers Arush Chhatrapati Henry M. Gunn High School (joining UC Berkeley, Fall 2021) Palo Alto, CA, USA [email protected] July 28, 2021 Abstract In this compilational work, we combine various techniques from classical cryptography and steganog- raphy to construct ciphers that conceal multiple plaintexts in a single ciphertext. We name these \multi- ciphers". Most notably, we construct and analyze a Four-In-One-Cipher: the first cipher which conceals four separate plaintexts in a single ciphertext. Following a brief overview of classical cryptography and steganography, we consider strategies that can be used to creatively combine these two fields to construct multi-ciphers. Finally, we analyze three multi-ciphers which were constructed using the techniques described in this paper. This cryptanalysis relies on both traditional algorithms that are used to decode classical ciphers and new algorithms which we use to extract the additional plaintexts concealed by the multi-ciphers. We implement these algorithms in Python, and provide code snippets. The primary goal of this work is to inform others who might be otherwise unfamiliar with the fields of classical cryptography and steganography from a new perspective which lies at the intersection of these two fields. The ideas presented in this paper could prove useful in teaching cryptography, statistics, mathematics, and computer science to future generations in a unique, interdisciplinary fashion. This work might also serve as a source of creative inspiration for other cipher-making, code-breaking enthusiasts. 1 Background and Related Work We briefly summarize relevant background information. Related work on the concept of a \multi-cipher" is referenced in 1.4.