# Ch 7 A Cryptography Who was Alan Turing

- Slides: 26

Ch 7 A Cryptography

Who was Alan Turing and what was the Enigma machine? • Alan Turing (1912– 1954) was a British mathematician and computer scientist. • He is most famous for solving the German naval Enigma code during World War II. • During World War II, the Germans used the Enigma, a cipher machine, to develop nearly unbreakable codes for sending secret messages. The Enigma's settings offered 150, 000, 000 possible solutions, • Also known for what is now dubbed the “Turing Test. ” It is a process of testing a machine’s ability to “think. ” • The basic premise of the Turing Test is that a human judge would be placed in isolation and have two conversations - one with a computer and one with another person. If the computer could fool the judge and carry on a conversation that is indistinguishable from that of the human, the computer is said to have passed the Turing Test.

What is Cryptography? Cryptography is the study of how to convert messages into code (encryption) and how to solve codes (decryption). Just as TCP enables reliable transmission over an unreliable network, cryptography enables verifiable, secure transmission over an insecure network. • Symmetric cryptography uses the same secret key to encode and to decode a message. • Asymmetric cryptography uses two different keys for encryption and decryption, so sharing the public encryption key doesn't give away the private decryption key.

What is Encryption? • Encryption transforms a message or data file in such a way that the contents are hidden from unauthorized readers. • Ciphertext is an encrypted message or file • Plain text aka “clear text” is an original message that has not yet been encrypted. In technical terms, Encryption is process of converting plaintext into ciphertext. Decryption is the process of converting ciphertext into plaintext

How is Data Encrypted? • Data is encrypted by using a cryptographic algorithm and a key. • It is commonly applied to data packets, bank card numbers, confidential emails, and individual files with sensitive info. • A cryptographic algorithm is a procedure for encryption or decryption. • A cryptographic key is a word, number, or phrase that must be known to encrypt or decrypt data.

The current worldwide standard is AES (advanced Encryption Standard). It is possible to crack AES but difficult and requires a lot of computer power.

Encryption Process of unscrambling the message to make it readable 256 Symmetric encryption Cesar’s Cipher algorithm Asymmetric encryption SSL TLS KEY Reasonable time Public key encryption

In Summary… If Bob wants to send Alice a secret message, he enciphers it with Alice's public key. Then no one else can decipher it, even knowing her public key. Only her private key can undo the encryption, and you can't figure out the private key from the public key.

What are Authentication protocols? • Authentication protocols include passwords, PINs, and fingerprint scanners as the first line of defense. • i. Phones and i. Pads should be configured to require a login, called a password. When the devices are password protected, the contents of the storage volume are automatically encrypted.

• Android devices have an overwhelming amount of security settings. • Do not automatically encrypt data stored on the devise when a password is activated. Follow these steps to change this:

For Windows and OSx see pg 450 -451 in textbook

FOR HW: Khan Academy Quiz next class If you have time, I suggest all of these! I am “assigning”/”quizzing” you on 1) What is Cryptography? 2) The Cesar Cipher, 3) Cesar Cipher Exploration, 4) Frequency Fingerprint Exploration 5) Polyalphabetic cipher 6) Polyalphabetic cipher exploration and 7) the Enigma encryption machine

Password Intro Video

What is a strong password? • A strong password is difficult to hack. Convention tells us that passwords are at least 8 characters, include one or more uppercase letters numbers, and symbols.

More advice from your textbook in creating passwords …

How can Hackers get my password? • A brute force attack uses password cracking software to generate every possible combination of letters, numerals, and symbols. • Can run for days before a password is cracked. • A dictionary attack helps hackers guess your password by going through dictionaries in common languages. • These also include mutated words such as p@ssw 0 rd

What make a password susceptible to a hacker? • Words from a dictionary • Doubled words like computer - • Default words like password, admin, system, and guest • Words with a string of numbers at the end • Words with symbol or numeric mutations such as v 01 dem 0 rt • Sequences of numbers formatted as phone numbers or dates • Conventional capitalization • Usernames

How can we determine how many possible passwords we would have? •

EXAMPLE 2 How many possibilities could an eight-character password with uppercase letters, lowercase letters, and numbers have? What if your NOT allowed to repeat?

Notice that the number of bits does NOT refer to the length of the password. EX: an i. Phone’s passcode is 4 digits in length, but entropy is rounded up to 4. The number 14 enumerates how many bits are needed to represent the number of possible passcodes in binary. The takeaway about entropy is that passwords with higher entropy are more secure than passwords with low entropy. A 46 -bit password, therefore, is far more secure than a 13 -bit password. Also, entropy is a theoretical concept. In the real world, security measures may be in place to prevent hacking tools from trying a continuous stream of passwords.

Quick Quizzes!

Khan Academy Quiz

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