Web Tools for Classical Cryptology

Tristan Beeble

Overview

Background Types of problems Tools

Cryptology

Cryptography– Encoding a message

Cryptoanalysis– Decoding a message

Background

Client: Professor Lesh Gen-ed Math course Help solve homework problems

Goals

Decoding Additional study Aid, not solve Easy to use

Terms

Plaintext: Message you want to send Ciphertext: Actual text sent Key: What’s needed to decode Algorithm: How to decode Cipher: allowed plaintexts, keyspace,

encryption and decryption algorithm

Types of Ciphers

Caesar Cipher Monoalphabetic Ciphers Polyalphabetic Ciphers

– Vigenère Cipher

Caesar Cipher

Plaintext: tristan

Key: 7

Ciphertext: aypzahu

Monoalphabetic Cipher

Caesar

Plaintext: A B C D E

Ciphertext: B C D E F

Monoalphabetic

Plaintext: A B C D E

Ciphertext: E C A B D

Monoalphabetic cipher

Polyalphabetic Cipher

Vigenère cipher

Plaintext: i n i t i a t e

Key: u n i o n u n i

Vigenère cipher

Vigenère Cipher

Plaintext: i n i t i a t e

Key: u n i o n u n i

Ciphertext: c a q h v u g m

Caesar Cipher Decryption

Same idea as Encryption Backwards

Ciphertext: aypzahu

Key: 7(-7)

Plaintext: tristan

Caesar Cipher Tool

Caesar Cipher Tool

Monoalphabetic Cipher Decryption

First Step:Guess work– Word length– Partial solutions

Second Step:Frequency Analysis

Frequency analysis

Frequency Analysis Tool

Monoalphabetic Cipher Tool

e

lmstn qtomq ***e* te**t

t

Vigenère Cipher Decryption

Repeated Segments Factors

– Plaintext: the bird ate the cat– Key: uni onun ion uni onu– Cipher: num pvlq ihr num qnn

10

Multiple Frequency Analysis

Vigenère Cipher Tools

fgsjetladkjdjkeifldlkowfgewsloiodkjplkjhgfetllk

DJK 21

Repeated Substrings

T H B Z T H B T

T 1 0 0 0 1 0 0 1

H 0 2 0 0 0 2 0 0

B 0 0 3 0 0 0 3 0

Z 0 0 0 4 0 0 0 0

T 1 0 0 0 5 0 0 1

H 0 2 0 0 0 6 0 0

B 0 0 3 0 0 0 7 0

T 1 0 0 0 1 0 0 8

Repeated substring started

Repeated substring ended

Vigenère Cipher Tools

Future work

Encryption More types of Ciphers

Accomplishments

Save the student time Allow them to do more Easier for the professor More complex examples

Questions?