Hashing and Encryption

What do many logical security controls depend on to some extent?

Encryption technologies

When is a message encrypted by a cipher only readable?

When the recipient has the correct key for that cipher

What does the use of encryption allow sensitive data to do?

Travel across a public network, such as the Internet, and remain private

What are the three principal types of cryptographic technology?

Symmetric encryption, asymmetric encryption, and cryptographic hashing

What does a symmetric encryption cipher use?

A single secret key to both encrypt and decrypt data

Why is the secret key in symmetric encryption called secret?

It must be kept secret

What happens if the symmetric key is lost or stolen?

The security is breached

What is the main problem with symmetric encryption?

Secure distribution and storage of the key

How does the key distribution problem change as the key's distribution needs become more widespread?

It becomes exponentially greater

What is the main advantage of symmetric encryption?

Speed

What can a symmetric cipher such as AES do efficiently?

Bulk encryption and decryption of multiple streams of data

What does an asymmetric encryption cipher use?

A key pair

What is a key pair in asymmetric encryption?

A private key and a public key that are mathematically linked

For any given message, what can either key do in asymmetric encryption?

Perform either the encrypt or decrypt operation but not both

What can reverse an operation in asymmetric encryption?

Only the paired key

If the public key is used to encrypt a message, which key can decrypt it?

The linked private key

Can the public key decrypt what it has just encrypted?

No

If the private key is used to encrypt something, which key can decrypt it?

The public key

What is the key point about one type of key in asymmetric encryption?

It cannot reverse the operation it has just performed

Who should know the private key?

A single subject

How can the public key be distributed?

Widely and safely to anyone with whom the subject wants to communicate

Can the private key be derived from the public key?

No

What is a hash?

A short representation of data

What does a hash function do?

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

What makes a cryptographic hash a one-way function?

It makes it impossible to recover the original value from the hash

What are cryptographic hashes used for?

Secure storage of data where the original meaning does not have to be recovered

What example does the text give for cryptographic hash use?

Passwords

Which cryptographic hash algorithm family is perhaps the most used?

Secure Hash Algorithm (SHA)

Which SHA versions does the text say are the most used?

SHA-256 and SHA-3