4-rto rpo, cryptography intro (symmetric algorithms)

Recovery Time Objective (RTO)

Maximum amount of time that it should take to recover a service after a disaster

Recovery Point Objective (RPO)

Maximum time period from which data may be lost in the wake of a disaster

Recovery service level (RSL)

Percentage of a service that must be available during disaster

Differential backup

Includes all data that has changed since last full backup

Incremental backup

Includes data that has changed since last full or incremental backup

Hot site

Fully operational data centers stocked with equipment and data, available at a moments notice

Cold site

Empty data centers stocked with core equipment and relatively inexpensive

Warm sites

In-between hot and cold. Somewhat stocked

Read through disaster recovery test

Read through procedures and team provides feedback

Walk through/table top excersize

Gathers the team together for a formal review of the disaster recovery plan

Simulation test disaster recovery

Uses a practice scenario to test the disaster recovery pan

Parallel disaster recovery test

Activates the disaster recovery environment but does not switch operations there

Full interruption test

Switches primary operations to the alternate environment

After action report

Creates a formal record of a disaster recovery (DR) or business continuity (BC) event

Code

A system that substitutes one word or phrase for another, codes are intended to provide secrecy/ efficiency

Cipher

A system that uses mathematical algorithms to encrypt and decrypt messages

Stream cipher

Operates on one character or bit of a message at a time

Block cipher

Operates on large segments of the message at the same time

Substitution cipher

Changes the characters in a message. Wx: ROT13

Transposition cipher

Rearranges the characters in a message

NIST cryptographic life cycle

1. Initiation

2. Acquisition/development

3. Implementation/assessment

4. Operation/maintenance

5. Disposition (sunset)

If Alice wants to send a message to Bob using symmetric cryptography, what key does she use to encrypt the message?

Shared secret key

3DES

• Symmetric encryption algorithm

• Block cipher operating on 64 bit blocks

• Effective key length of 112 bits

• Is weak being phased out

Advanced Encryption standard (AES)

• Considered secure

• Block cipher operating on 128 bit blocks

• Key length of 128, 192, or 256 bits

Blowfish

• Symmetric encryption algorithm

• Block cipher operating on 64 bit blocks

• Key length between 32 bit and 448 bit

• Not secure anymore

Twofish

• Symmetric algorithm using a block cipher operating on 128 bit blocks

• Key length of 128, 192, or 256 bits

• Secure

RC4

• Not secure anymore

• Symmetric algorithm

• Stream cipher

• Variable key length between 40 and 2048 bits

What basic cryptographic functions does the AES algorithm use to encrypt plaintext?

Both substitution and transposition