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Cipher Toolkit: Decrypt Standard Ciphers with Statistical Analysis

Cipher is a software toolkit aiding in decryption of historical ciphers. It provides statistical data and analysis on encrypted messages, serving as a learning tool for amateur cryptographers. Includes substitution ciphers and transposition ciphers like Vigenère. Explore monoalphabetic and polyalphabetic ciphers, frequency analysis, and examples like Caesar shift cipher. Transform plaintext to ciphertext and learn encryption methods with this toolkit.

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Cipher Toolkit: Decrypt Standard Ciphers with Statistical Analysis

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  1. CYPHER INDEX • Introduction • Background • Demo

  2. INTRODUCTION • Cypher is a software toolkit designed to aid in the decryption of standard (historical) ciphers by providing statistical data and algorithmic analysis on encrypted messages. • This toolkit hopes to serve as a cryptographic learning tool and as a past time for amateur cryptographers.

  3. BACKGROUND • Substitution ciphers are characterized by a substitution of a character in the original plain text message by the corresponding character in the cipher alphabet, often according to some protocol derived from a predetermined key. • Transposition ciphers retain a characters true form but instead change its position.

  4. Substitution Ciphers • Monoalphabetic Substitution Ciphers • Polyalphabetic Substitution Ciphers

  5. Monoalphabetic Substitution • In a monoalphabetic substitution cipher, a single character in the plain text alphabet is replaced by a single character in the cipher alphabet. • Frequency Analysis is a key to solve monoalphabetic substitution cipher.

  6. Monoalphabetic Substitution • Frequency example • E - 12.3% • T - 9.6% • A - 8.0% • O - 7.94% • N - 7.19% • I - 7.18%

  7. Monoalphabetic Substitution • Plain alphabetabcdefghijklmnopqrstuvwxyz • Cipher alphabetxzavoidbygerspcfhjklmnqtuw

  8. Polyalphabetic Substitution • Multiple cipher alphabets are used in Polyalphabetic Substitution. • Vigenère cipher is the simplest type of polyalphabetic cipher.

  9. Keyword Plaintext Ciphertext W H I T E W H I T E W H I T E W H I T E W H I D I V E R T T R O O P S T O E A S T R I D G E Z P D X V P A Z H S L Z B H I W Z B K M Z N M Vigenère Cipher

  10. Transposition Ciphers • Transposition cipher rearranges the positions of the characters but not their true values, so that a frequency analysis of a message encrypted by transposition appears "normal". • Rotating columns and/or rows of the message, rotating the entire message left or right, or along diagonals.

  11. Transposition Ciphers • Plaintext: The day is coming to an end, and • Ciphertext:TDIOHASMEYCI NOE,GANATNDN

  12. Other Ciphers • Ceaser shift cipher • Plaintext : abcdefghijklmnopqrstuvwxyz • Ciphertext: defghijklmnopqrstuvwxyzabc • Encrypt a message is by using a key-text, such as the Declaration of Independence or a well-known poem, numbering the words in the said document and replacing letters in the plaintext by a number that represents the first character of that number word in the key-text.

  13. Demo

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