History of Cryptography

Cryptography comes from the Greek meaning 'hidden writing.'

Steganography is the practice of covered writing to conceal a message. It was used in ancient times to hide information during communication.

The two subtypes of cryptography are transposition and substitution. Transposition rearranges the letters in a message, while substitution replaces the letters altogether.

<p>The Spartans used a device called a skytale, which consisted of a strip of leather wrapped around a wooden rod. The message was written on the leather and became clear when wrapped around an identical rod.</p> Signup and view all the answers

<p>The Caesar cipher is a substitution cipher that replaces any given letter with the letter three spaces down the alphabet. It works by shifting the alphabet by a fixed number of positions.</p> Signup and view all the answers

<p>A short message has a limited number of scramblings, and larger messages become too difficult for the intended receiver to disentangle.</p> Signup and view all the answers

<p>There are 25 variations of the Caesar cipher. It is not secure against brute force attacks because a code breaker could check all 25 shifts to decrypt the message.</p> Signup and view all the answers

<p>The advantage of a keyword cipher is that it is more secure and easier for the sender and receiver to remember, as it uses a keyword to construct the cipher alphabet.</p> Signup and view all the answers

<p>A totally random arrangement of the alphabet would be difficult for the receiver to remember. It would also be challenging for a code breaker to decipher without the specific arrangement key.</p> Signup and view all the answers

<p>The shift value determines the number of positions the alphabet is shifted. There are 25 possible shift values in the Caesar cipher.</p> Signup and view all the answers

<p>The skytale was used to hide military communications by transposing the message. It functioned by wrapping a leather strip around a wooden rod, making the message clear when unwrapped around an identical rod.</p> Signup and view all the answers

<p>Steganography involves covering writing to conceal a message, but if the message is discovered, its contents will be easily revealed. This limitation led to the invention of cryptography, which hides the meaning of a message instead of its existence.</p> Signup and view all the answers

<p>Steganography hides the existence of a message while cryptography hides the meaning of a message.</p> Signup and view all the answers

<p>It limits the number of possible scramblings for shorter messages, making it difficult for the intended receiver to decode.</p> Signup and view all the answers

<p>Keyword ciphers are more resistant to brute force attacks compared to Caesar ciphers.</p> Signup and view all the answers

<p>It leads to a limited number of permutations, making it vulnerable to brute force attacks.</p> Signup and view all the answers

<p>To make a message appear as a jumble of letters, which became clear when wrapped around an identical rod.</p> Signup and view all the answers

<p>A keyword cipher allows for easy memorization and retrieval compared to a totally random arrangement.</p> Signup and view all the answers

<p>It was used by Julius Caesar during the Golic wars to conceal military communications.</p> Signup and view all the answers

<p>It revealed the existence of messages if discovered, allowing interceptors to easily understand their contents.</p> Signup and view all the answers

<p>It allows for a larger number of possible permutations, making it more resistant to brute force attacks.</p> Signup and view all the answers

<p>Identification of the repetition of the keyword in the Vigenere cipher by Charles Babbage</p> Signup and view all the answers

<p>Complexity and use of multiple Caesar alphabets</p> Signup and view all the answers

<p>Homophonic substitution ciphers</p> Signup and view all the answers