Domain 3: Cryptography Flashcards
What is Plaintext?
An unencrypted message
What is Ciphertext?
an Encrypted message
What is Cryptology?
the science of secure communications
What is Symmetric Encryption?
Encryption that uses one key encrypt and decrypt
What is Asymmetric Encryption?
Encryption that uses two keys; if you encrypt with one, you may decrypt the other.
What is a Cryptography?
creates messages whose meaning is hidden
What is a Cryptanalysis?
the science of breaking Encrypted message
It is important to remember that Cryptology encompasses two disciplines. what are they?
Cryptography
Cryptanalysis
What is a Cipher?
A Cryptographic algorithm
What is a Plaintext?
An unencrypted message
What is a Encryption?
Converts Plaintext into Ciphertext
Cryptography provides which parts of Confidentiality Integrity Availability (CIA)
Confidentiality
Integrity
but not Availability
Cryptography provides which parts of Identity - Authentication - Authorization – Accountability: IAAA)
Proving an Identity Claim
Identity - Authentication
but not Availability
can Cryptography provide Non-repudiation?
Yes
What is Confusion?
The relationship between the Plaintext and the Ciphertext should be as random (Confused) as possible.
What is Permutation?
Provides Confusion by rearranging the Plaintext anagram-style
What is Diffusion?
The order of the Plaintext should be dispersed (Diffused) in the Ciphertext.
Are Permutation and Substitution are often combined?
Yes
What is Substitution?
Provides diffusion by replacing one character for another
What should Strong Encryption accomplish?
Should destroy patterns.
What metric is used to determine if a cipher uses strong encryption?
If a single bit of Plaintext changes, the odds that all of the bits of the resulting Ciphertext should be 50% or greater.
What do Cryptanalysts look for to break an encryption?
Any signs of nonrandomness may be used as clues to a Cryptanalyst.
In Cryptanalysis what is the Work Factor?
Describes how long it will take to break a cryptosystem.
In Cryptanalysis, what is Breaking a Cryptosystem:
Decrypting Ciphertext without a key
Does Secrecy of the cryptographic algorithm provide strength?
No
What is a Monoalphabetic Ciphers:
Uses one alphabet for substitution.
What is a weakness to Monoalphabetic Ciphers?
Susceptible to Frequency Analysis
What is a Polyalphabetic Cipher?
Uses multiple alphabets for substitution.
What is Frequency Analysis?
The study of the frequency of letters or groups of letters in a ciphertext.
What is Modular Math?
It shows you the remainder
What is another name for Modular Math?
Clock Math
Why is Modular Math Cryptology?
is is the underlying math behind a lot Cryptography.
What does Exclisive OR mean?
A Boolean operator that returns a value of TRUE only if both its operands have different values.
an exclusive OR means “this or that, but not both.”
An exclusive OR is often called an XOR or EOR.
What does XOR stand for?
Exclusive Or
What is the First known example of secret writing
Egyptian Hieroglyphics
What is Egyptian Hieroglyphics?
Stylized pictorial writing used in ancient Egypt.; Some contained small puzzles
What is Spartan Scytale?
Used in Ancient Sparta around 400 BC
A strip of parchment wrapped around a rod.
Plaintext written lengthwise down the rod.When unwound, the parchment was unreadable
The receiver possessed a rod of equal length and diameter.
What is a Rotation Ciphers ?
Used by Gaius Julius Caesar; rotated each letter of the plaintext three times to encrypt (A became D)
What is a another name for a Rotation Ciphers ?
Caesar Cipher
What is a Vigenére Ciphers?
A Polyalphabetic rotational Cipher named after Blaise de Vigenére
How does a Vigenére Ciphers work?
It consists of the alphabet written out 26 times in different rows, each alphabet shifted cyclically to the left compared to the previous alphabet, corresponding to the 26 possible Caesar ciphers.
Top Row holds the plaintext
Left Column holds the Ciphertext
The person sending the message chooses a keyword and repeats it until it matches the length of the plaintext
is the Vigenére Ciphers a Polyalphabetic Cipher or a Monoalphabetic Cipher?
Polyalphabetic Cipher
How do you encrypt with a Vigenére Ciphers ?
How do you decrypt with a Vigenére Ciphers ?
What is a Cipher Disk?
Two concentric disks with an alphabet around the periphery.
What is a Monoalphabetic Cipher Disk?
Two parties agree on a fixed offset: Set S to D.
What is a Polyalphabetic Cipher Disk?
Same as Monoalphabetic,
Two parties agree on a fixed offset: Set S to D.
but then the two parties agree to turn the wheel every X characters.
What is a a set of Jefferson Disks?
36 Wooden Disks each with 26 letters in random order.
How do you encrypt with Jefferson Disks?
Arrange the first 36 letters along one line on the disks
Pick any other line and write down the Ciphertext
What is a Book cipher?
Uses whole words from a well known text.
How do you decrypt with Jefferson Disks?
Arrange the Ciphertext along one line on the disks
The recipient looks at all other 25 lines for something that makes sense.
How do you encrypt with a Book cipher?
Agree on a text
For each word in the plain text, note the
Page Number
Line
Word offset
Example from Benedict Arnold to Nathan Bailey
As 158.9.25 and 115.9.12 are 226.9.3
As Life and Fortune are risked
What is a Running Key Cipher?
Uses a well known text but uses modulus math to add letters to each other
How do you encrypt with a Running Key Cipher?
What is a Code Book?
Assign a code word for important people, locations and terms. In some cases, assign more than one code word.
What is a One Time Pad?
Uses identical paired pads of random characters with a set amount of characters on each page.
How do you encrypt with a One Time Pad?
Align the plaintext along the random characters and perform modulo math.
What is the only encryption method that is mathematically proven to be secure?
One-Time Pad
What are the three prerequisites to ensure that one-time pads are the only encryption method that is mathematically proven to be secure?
1: If the characters are truly random,
2: The pads are kept secure
3: No one page is ever re-used.
What is a Vernam Cipher?
A teletypewriter that encrypted and decrypted using paper rolls as the one time pad.
The bits were XORd
First known use invented by Gilbert Vernam in 1917.
Why does Brute Forcing One-Time Pads not work?
Since the key of a one-time-pad is the same length as the Plaintext, brute forcing every possible key will eventually recover the Plaintext, but it will also produce vast quantities of other potential Plaintexts including the works of Shakespear.
What is a Hebern Machines ?
The Hebern Rotor Machine was an electro-mechanical encryption machine built by combining the mechanical parts of a standard typewriter with the electrical parts of an electric typewriter, connecting the two through a scrambler.
It is the first example (though just barely) of a class of machines known as rotor machines that would became the primary form of encryption during World War II and for some time after, and which included such famous examples as the German Enigma.
A Hebern Machine is what kind of encryption machine?
Rotor Machine
What is the Enigma machine?
A Rotor Encryption machine that used three finger wheels that could be set to any number from 1-26
used by the Germans in WWII.
How do you encrypt with an Enigma machine?
type the plaintext into the typewriter. The wheels will turn and a lamp illuminated with the Ciphertext.
How do you decrypt with an Enigma machine?
set the wheels to the original position and type the Ciphertext. The lamp will illuminate the plaintext.
What is the SIGBA machine?
Improvement to the Enigma used by the US.
Never broken.
What is the Purple (Red and Jade) machine?
Rotor-like device used by the Japanese
Actually a stepping switch device
How did the intelligence community view the technology behind cryptanalysis
Arguably as powerful as any bomb and tried to regulate it through the same munitions laws.
Why is the Coordinating Committee for Multilateral Export Controls (COCOM) important?
Designed to control the export of critical technologies to Iron Curtain countries between 1947 and 1994.
Export of encryption technologies by members to non-COCOM countries (US, Australia, Turkey, non-soviet union countries in Europe) was heavily restricted.
What does COCOM stand for?
The Coordinating Committee for Multilateral Export Controls
What is the Wassenaar arrangement?
Created in 1996 after COCOM ended, it included many more countries including former soviet union countries and greatly relaxed the restrictions on exporting cryptography.
