L16 - T16A - S9 – Hashing and Encryption Concepts

True

True or False: A message encrypted by a cipher is only readable if the recipient has the correct key for that cipher

The 3 principal types of cryptographic technology

• Symmetric encryption

• Asymmetric encryption

• Cryptographic hashing

Hash

• Short representation of data

• Takes any amount of data as input and produces a fixed-length value as output

  • Cryptographic [answer] performs this process as a one-way function that makes it impossible to recover the original value from the hash

    • used for secure storage of data where the original meaning does not have to be recovered (passwords, for instance)

2 of the most used cryptographic hash algorithms

• Secure Hash Algorithm (SHA) and  

• Message Digest (MD5) 

  • MD5 is the older algorithm and is gradually being phased out of use 

Symmetric Encryption Cipher (aka shared-key encryption)

• Uses a single secret key to both encrypt and decrypt data

  • Secret key must be kept secret - if stolen or lost = security breached

• Main Advantage

  • Speed

    • A symmetric cipher, such as the Advanced Encryption Standard (AES), can perform bulk encryption and decryption of multiple streams of data efficiently 

• Main Problem

  • Secure distribution and storage of the key

  • Exponentially greater the more widespread the key's distribution needs to be

Asymmetric Encryption Cipher

Cryptographic method that uses a pair of keys: a public key for encryption and a private key for decryption which are mathematically linked — (Google)

• Either key can perform either the encrypt or decrypt operation but not both

  • Only paired key can reverse the operation

• Main drawback

  • A message cannot be larger than the key size

Typical mathematical algorithms to link keys

• Rivel,

• Shamir,

• Adleman (RSA) or

• Elliptic curve cryptography (ECC) algorithms

Private Key (Asymmetric Encryption)

This key is known only to the holder and is linked to, but not derivable from, a public key distributed to those with which the holder wants to communicate securely — (A+)

• Must be kept a secret known only to a single subject (user or computer)

Public Key (Asymmetric Encryption)

This key is freely distributed and can be used to perform the reverse encryption or decryption operation of the linked private key in the pair – (A+)

• Can be widely and safely distributed to anyone with whom the subject wants to communicate

• Private key cannot eb derived from it