Cryptography

Question 1

Hashing

Answer 1

Hashing algorithms create hexcode strings of a fixed length. The length is determined by the algorithm. Hashing is oneway encryption. Cannot be decrypted. Hash strings are hexadecimal.

Question 2

What is hexadecimal?

Answer 2

It is a shorthand for binary (0s and 1s) where each hex character represents a permutation of a group of four 1s and 0s. 0 1 2 3 4 5 6 7 8 9 a b c d e f

Question 3

Explain binary

Answer 3

Each number is a bit (0 or 1)
8 bits = byte
1024 bytes = kilobyte
1024 kilobytes = megabyte
1024 megabytes = gigabyte
1024 gigabytes = terabyte

Question 4

Explain hashing digest

Answer 4

A hashing algorithm has a digest, measured in bits as size, which is the hex-code string x 4. The digest is the binary representation of the hex code. Two completely different values could theoretically create the same digest, which is called a collision.

Question 5

File and hashing

Answer 5

A file can be hashed. This is because a file is 1s and 0s (binary). Everything in computer world is long strings of 1s and 0s.

Question 6

What is the best algorithm for encryption?

Answer 6

AES

Question 7

Hashing algorithms

Answer 7

md5
sha1
sha2
sha-128 (128 bit digest), sha-256 (256 bit digest)

Question 8

What is symmetric encryption?

Answer 8

The idea is that an algorithm is used to encrypt and decrypt clear text into cipher text, using a secret key.

The key is converted to binary, and the clear text as well. This is used by the algorithm to create the cipher text. Most current algorithms are BLOCK CIPHER ENCRYPTION where chunks of bits are encrypted by having key as binary+chunk (which is binary), encrypted chunk by chunk and the cipher text is the concatenation of all these cipher text strings for each chunk of data.

Different algorithms use different chunk sizes - like 256 bits or whatever.