Cryptography

Question 1

Encryption vs Encoding

Answer 1

Encoding - transformation of data to be used on a different system
not secret
Encryption - secret

Question 2

Define a Stream Cypher vs a Block Cypher

Answer 2

Stream encrypts one bit at a time

Block encrypts one block at a time.

Question 3

Define Confidentiality

Answer 3

Confidentiality is the protection of information such that only the originator and intended recipients can see the information. In essence this means data is being encrypted.

Question 4

Define Authentication

Answer 4

Authentication is where the identity or authenticity of an entity (such as a user logging into a PC) is verified. The entity could be a user, message or device. User/message authentication normally pertains to the checking of a user’s/originators claimed identity.

Question 5

Define Integrity (data).

Answer 5

Integrity involves mechanisms that ensure that if data has been modified, changed or deleted, the modification can be detected. This includes detection of anyone attempting to insert data into communications traffic.

Question 6

Define non-repudiation.

Answer 6

Non-repudiation protects against one party in a communication exchange claiming that it never occurred. There are various forms of non-repudiation, including non-repudiation of origin and non- repudiation of receipt.

Question 7

Define DES

Answer 7

Data Encryption Standard
was the first common digital encryption algorithm used extensively by businesses rather than governments.
Now obsolete

Question 8

Define 3DES

Answer 8

Triple DES was brought in after some weaknesses were found in DES, but purely as a stopgap until a brand new algorithm could be developed and standardised. Now obsolete.

Question 9

Define AES

Answer 9

The Advanced Encryption Standard. Symmetric Key Algorithm.

Only publicly accessible cypher approved by the NSA

Question 10

Define RSA

Answer 10

Asymmetric Cryptography Algorithm
Rivest–Shamir–Adleman

It is based on the principle that it is easy to multiply large numbers, but factoring large numbers is very difficult. For example, it is easy to check that 31 and 37 multiply to 1147, but trying to find the factors of 1147 is a much longer process.

Question 11

Define MD5

Answer 11

Message Digest Algorithm
One way.
Not collision free so not recommended for use.

Question 12

Define SHA

Answer 12

Secure Hashing Algorithm
Available in SHA 1,2 and 3
1 is no longer used.
2 and 3 are collision free.

Question 13

Define HMAC

Answer 13

Hash-Based Message Authentication Code