Domain Six: PKI and Cryptography Flashcards
What are the PAIN concepts that ryptography should address ?
Privacy, Authentication, Integrity, Non - Repudiation
What is Data in Use ?
This is data that is actively in use by the computer system. This includes data stored in memory while being processed.
What is the main protection for data in transit ?
Encyption via tls
What is data at rest ?
Data that is stored in storage media - encryption is an obvious protection
What is a cipher ?
The actual algorithm used to carry out cryptography
What are the two categories that ciphers fall into ?
Block and Stream
What is the advantage of block ciphers ?
High diffusion and immune to insertion
What is the disadvantage of block ciphers ?
Slow and error propagation
What is the advantage of stream ciphers ?
Speed and low error propagation
What are the disadvantages of stream ciphers ?
Low diffusion and susceptibiltiy to malicious insertion
What is a block cipher ?
Encrypts data in whole or in chunks and used when we know the size of the data to be encrypted
What is a stream cipher ?
Encrypts each individual bit as part of a stream
What is the concept of confusion in cryptography ?
Makes the relationship between the cipher and data as complex as possible. Confusion means that each binary digit (bit) of the ciphertext should depend on several parts of the key, obscuring the connections between the two.[3]
The property of confusion hides the relationship between the ciphertext and the key.
This property makes it difficult to find the key from the ciphertext and if a single bit in a key is changed, the calculation of most or all of the bits in the ciphertext will be affected.
What is the concept of diffusion in cryptography ?
Diffusion means that if we change a single bit of the plaintext, then about half of the bits in the ciphertext should change, and similarly, if we change one bit of the ciphertext, then about half of the plaintext bits should change.[5] This is equivalent to the expectation that encryption schemes exhibit an avalanche effect.
The purpose of diffusion is to hide the statistical relationship between the ciphertext and the plain text
What kind of algorithm is DiffieHelman ?
Asymmetric
What kind of algorithm is DSA ?
Asymmetric - Good for digital signatures but does little for confidentiality
What kind of algorithm is Elliptical Curve ?
Asymmetric - Very fast uses real and rational numbers and requires smaller key sizes to provide same security as other algorithms
What kind of algorithm is RSA ?
Standard for Asymmetric - Key 2048 bits
What kind of agorithm is 3DES ?
Symmetric - Comes in four different types and the key length is 112 to 168 256 and 356. The different flavours use a key multiple times
DES - EEE2 Two key are used in the encryption process three times
DES - EDE2 Two key are used in the encryption process twice and once in the decryption process
DES - EEE3 Three keys are used in the encryption process three times
DES - EDE3 Three key are used in the encryption process twice and once in the decryption process
What kind of algorithm is AES ?
Symmetric - 3DES was only ever a stopgap and AES was the preferred standard and was based on the Rijndael algorithm. The key lengths are 128, 192 or 256 bits
What kind of algorithm is DES ?
Symmetric - DES uses a 64 bit key but 8 bits are used for parity checking so in actuality the key is only 56bits. This is a deprecated mechanism because it was shown that the algorithm could be cracked in less that 24 hours.
What kind of algorithm is RC4 ?
Symmetric - Ron Rivest came up with these ciphers. They are fast steam ciphers which are perfect for WiFi WEP. The key length is 40 bits plus a 24 bit initialisation vector making it 64 in total length.
What is a cipher mode ?
These are the primary ways of using the ciphers that adds additional functionality. So you would never use AES on its own but in conjunction with a cipher mode.
Describe the ECB cipher mode ?
Electronic Block will pad when there is a partial block. It is the easiest mode to break and is the native mode of DES. Its advantage is that it provides the highest throughput.
What is Cipher Block Chaining mode ?
Very similar to ECB has a slightly higher error rate meaning some block could become undecipherable.
What are counter cipher modes ?
Turns block ciphers into stream ciphers by the use of a counter function which is used alongside an IV.
What is Galois Counter Mode ?
Uses the Galois authentication with standard Counter Mode. Used specifically with 128 bit encryption
Describe the HMAC hashing algorithm ?
Designed to avoid collisions that other algorithms are prone to. This is done by the use of a shared private key but it does require that the key is sent out of bounds
What is MD5 ?
Hashing Algorithm - Takes a variable length input and produces a 128 bit output
What is the SHA algorithm ?
Hashing - SHA 1 and 0 are deprecated. SHA 2 is the most commonly used algorithm today
What is key stretching ?
Improving of weak keys for examples multiple rounds of either hashing or encryption
What is perfect forward secrecy ?
Used to change keys ensuring that even though a compromise occurs the blast radius is small.
What does the term east-west traffic mean ?
Lateral movement within a network