Expert answer:Cryptography
Solved by verified expert:For this assignment, you will write an essay on the video for this week:A Brief History of CryptographyIn this essay, discuss what you have learned on cryptography and how this method to secure information has changed over the decades. Provide a few examples of how cryptography actually secures data. In addition to the video, choose one other scholarly reference to support your discussion.Requirements:Submit in a Word document.Include cover pageMust be a minimum of two pages (excluding references and cover page)Appropriate APA format is required.Properly cite and reference any borrowed resource(s)Rubric
ContentProficient81 – 100 pointsAcceptable61 – 80 pointsBelow Standard0 – 60 pointsTotalContent is relevant, well-selected, and demonstrates good understanding of technologies that are required for this course.Content is somewhat relevant, well-selected, and demonstrates a general understanding of technologies that are required for this course.Content is not relevant, not well-selected, and does not demonstrate a general understanding of technologies that are required for this course.Grammar and FormatProficient81 – 100 pointsAcceptable61 – 80 pointsBelow Standard0 – 60 pointsContent demonstrates exceptional spelling and grammar. Content flows well and to enhance communication. Few or no errors that they do not impede overall readability.Content demonstrates acceptable spelling and grammar. Content flows well and to enhance communication. Few or no errors that they do not impede overall readability.Content does not demonstrate acceptable spelling and grammar. Content does not flow well and does not enhance communication. Multiple errors impede overall readability.
20171029185602chapter1_slides.pptx
20171029185606chapter2_slides.pptx
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FUNDAMENTALS OF CRYPTOGRAPHY
CHAPTER 1
The Purpose of Cryptography
• Protect information
• Confidentiality or secrecy of information
• Integrity allows for detection of changes in information
• Also provides services to
• Authentication
• Non-repudiation
Myths About Cryptography
• Its unbreakable
• Confusing mean encrypted
• All encryption is the same
• Encryption requires computers
• Encryption is hard
• New technology eliminates the need for encryption
Common Applications
• Hard drive encryption
• Microsoft Bitlocker, cipher, etc
• Digital signatures
• Ecommerce
• SSL, TLS
• Cell phones and communication devices
• Digital Rights Management (DRM)
Cryptography Fundamentals
• How encryption works
• Encryption converts plaintext to ciphertext
• Decryption converts ciphertext to plaintext
• Readable
Encryption
• Unreadable
• Transforms
Plaintext
Ciphertext
Introducing Algorithms
• What is an algorithm?
• Description of how a process works
• A formula or recipe
• Algorithms define how encryption or decryption is to be performed
• Algorithms are made up of ciphers
• Terms are used interchangeably
Example of an Encryption Algorithm
Note: Example is of an RSA based encryption algorithm
Methods of Encryption
Asymmetric
• Uses different key to encrypt and decrypt
• Not ideal for bulk data
• Slow on larger volumes of data
Symmetric
• Uses same key to encrypt and decrypt
• Ideal for large volumes of data (bulk data)
• Fast on large data sets
What is a Key?
• Represent a specific sequence for the encryption process
• Similar to combination of a lock
• Lock can have many possible combinations however only one is correct and
will open the lock
• The amount of possible keys defined by an algorithm is known as a
keyspace
Key (cont)
• Represents main strength of the system
• Strength relies on secrecy of key
• Only authorized parties have access to key
• Key length
• Typically the longer the stronger
• Complexity of key is also important
• Measure in bits
Examples of Key Lengths
Key Length
Strength
40-bit
Algorithms are of no use
56-bit
Algorithms offer privacy, but are vulnerable
64-bit
Algorithms are safe today but will be soon threatened as the technology
evolves
128-bit
Algorithms are almost unbreakable
256-bit
Algorithms are impossible
Examples of Keys
Power / Cost
40 Bits (5 Char)
56 Bits (7 Char)
64 Bits (8 Char)
128 Bits (16
Char)
Individual
1.4 Min
73 Days
50 Years
10×20 Years
Corporate
2 Sec
35 hours
1 Year
10×19 Years
Governments
0.2 Sec
3.5 Hours
37 Days
10×18 Years
Kerckhoff’s Principle
Secrecy of Key vs
Algorithm
Algorithm is made
public
Key is kept secret
Hashing
• Provides a strong and reliable way of validating a
message
• Does not encrypt plaintext
• Must use another algorithm to perform encryption
• Can function together with another encryption
algorithm to yield confidentiality
Message Digest Functions
• Message digest functions change information into a single fixed length number.
• Typically between 128 and 256 bits in length
• The resulting hash is influenced by using every component bit of the data input
• If any single bit is changed in the input of a message the resulting hash should change
over 50 percent
• Any input value should result in a unique hash
Data
Hashing
MD
Message Digest
Fundamentals of Cryptography
Chapter 2
History of Cryptography
• Oldest example
• Hieroglyphics
Hieroglyphics (cont)
Hieroglyphics (cont)
Scytale
• Popular with Spartans
• Example of what is known as Transposition Cipher
Caesar Cipher
•
•
Example of a Substitution Cipher
Vulnerable to frequency analysis
–
ETANORISH
Caesar Cipher Example
• Caesar Cipher
Polyalphabetic Cyphers
• In 1452 Lean Battista Alberti created the polyalphabetic substitution
cypher.
• Alberti is known as the father of Western cryptography
• Polyalphabetic substitution makes cryptanalysis harder because
multiple alphabets are used in the process.
• Vigenere cypher is a much more complex form of Alberti’s cypher.
• Vigenere used 26 alphabets (Alberti used 2)
• Go to http://cs.widener.edu/~chiffens/Eexplained.html to see an
example of how it works.
American Civil War
•
•
•
•
Telegraph created need for increased encryption
Complex substitutions and transposition ciphers
Flag signals
Ulysess S Grant attributed many Union victories to the
intelligence gained from codebreaking
Modern Examples (1900+)
• Enigma
• Ultra
• Purple Code
Enigma
• Used by World War II Germany
• Special version for Wehrmacht and Kriegsmarine
• Japanese created own version
Enigma Example
Enigma Rotors
Ultra vs. Enigma
•
Ultra: Allied forces initiative to overcome the Germany Enigma
code
•
•
•
Based in Bletchley Park in the UK
Worked on by 9000 people
Notably worked on by Alan Turing
•
Referenced in film “The Imitation Game”
Japanese Purple (JN-25)
• Variant of Enigma
• Did not use rotors
• Broken by US “Magic” program prior to the start of US entry into
WW2
• Intelligence gathered gave huge advantage to America during the
Battle of Midway
Purple Machine Example
1970s
• Data Encryption Standard (DES)
• RSA Algorithm
…
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