Cyber Security Exam Systems, Security, and
Competitive Advantage questions and answers
Cryptography
protects information even when it is not under your physical control
Uses of Encryption
Privacy, Authenticity, Integrity, Nonrepudiation
Nonrepudiation
Positive proof that a message or action originated with a certain party
Process of Encryption
Key & Plaintext in Algorithm which creates a ciphertext
Kerckhoff's Principle
We assume that threats are familiar with how our cryptography works
All security rests in a secret key
Types of Cryptanalysis
Known Ciphertext, or Ciphertext Only
,All we know is the ciphertext
Most difficult situation, but common
Known Plaintext
We know the plaintext to match some of the ciphertext encrypted with a particular key
Chosen Plaintext
We can choose some plaintext to encipher with our victim's cipher, and retrieve the
ciphertext
Replace each letter in a text by the 3rd letter following it in the alphabet
Caesar Cipher
Uses a series of different rotations
The "key" may be a word - each letter indicates a rotation
Vigenère Ciphers
Encrypted telegram from foreign secretary of the German empire to German
ambassador in Mexico
Zimmerman Telegram
Enigma Machine
Replaced letters as they were typed
Substitutions were computed using a key and a set of switches and rotors
, Computer-Based Encryption
DES and AES
DES supported how many bits
56-bits
AES supported how many bits
128 bits, 192 bits and 265 bits
Key stream
It is a stream of bits with these properties:
Attackers can't predict its contents in practice
All trusted recipients either
have a copy of the same key stream, or
they can reconstruct the key stream
One time pad
distribute the entire key stream to everyone
The most secret stream cipher
Use one bit of truly random bit stream for each bit of data to be encrypted
Sender and recipient must both share exactly the same key stream
Also works with decimal digits
A popular spy cipher
Competitive Advantage questions and answers
Cryptography
protects information even when it is not under your physical control
Uses of Encryption
Privacy, Authenticity, Integrity, Nonrepudiation
Nonrepudiation
Positive proof that a message or action originated with a certain party
Process of Encryption
Key & Plaintext in Algorithm which creates a ciphertext
Kerckhoff's Principle
We assume that threats are familiar with how our cryptography works
All security rests in a secret key
Types of Cryptanalysis
Known Ciphertext, or Ciphertext Only
,All we know is the ciphertext
Most difficult situation, but common
Known Plaintext
We know the plaintext to match some of the ciphertext encrypted with a particular key
Chosen Plaintext
We can choose some plaintext to encipher with our victim's cipher, and retrieve the
ciphertext
Replace each letter in a text by the 3rd letter following it in the alphabet
Caesar Cipher
Uses a series of different rotations
The "key" may be a word - each letter indicates a rotation
Vigenère Ciphers
Encrypted telegram from foreign secretary of the German empire to German
ambassador in Mexico
Zimmerman Telegram
Enigma Machine
Replaced letters as they were typed
Substitutions were computed using a key and a set of switches and rotors
, Computer-Based Encryption
DES and AES
DES supported how many bits
56-bits
AES supported how many bits
128 bits, 192 bits and 265 bits
Key stream
It is a stream of bits with these properties:
Attackers can't predict its contents in practice
All trusted recipients either
have a copy of the same key stream, or
they can reconstruct the key stream
One time pad
distribute the entire key stream to everyone
The most secret stream cipher
Use one bit of truly random bit stream for each bit of data to be encrypted
Sender and recipient must both share exactly the same key stream
Also works with decimal digits
A popular spy cipher
