exam 2

Hash Function (cont.)

Good cryptographic hash functions should have the following properties: - Be unable to compute hash value of two messages combined given their individual hash values. - Hash should be computed on the entire message. Two messages will never have the same value, unique

Which of the following best explains BIA

It is the process of analyzing all business functions to determine the effect of IT outages in business

cryptograohy originally used for secrecy now used for many applications

Prevent unauthorized disclosure of information - Prevent unauthorized access to information, computers, websites, applications, etc. - Detect tampering - Detect injection of false data - Detect deletion of data - Prevent repudiation

examples of detective

fire alarm, perimeter intrusion systems, door alarms

public key

freely shared and used by others to encrypt messages or verify digital signatures

Transposition Cipher

type of encryption method that rearranges the letters or characters of a message without changing the actual letters themselves

Purpose if Cryptography

• Protect sensitive information from disclosure. • Identify corruption or unauthorized change of information. • Make compromises too expensive or too time consuming.

Which of the following is TRUE regarding symmetric cryptography?

The same key is used by both the sender (encryptor) and receiver (decryptor)

Encryption Systems Subtopics

• Classical substitution ciphers • Transposition (permutation) ciphers • Polyalphabetic ciphers • Running key cipher • One-time pad • Concealment • Steganography • Codes

public key vs private key

Public key you don't keep to yourself Private key is kept to your self

ciphertext/cryptogram

scrambled data

Symmetric key( private key/single key/secret key)

single key shared by originator and receiver. the algorithms include Rijndael, DES, Triple DES, Blowfish, IDEA, RC4, RC6, SAFER, Serpent, Twofish, etc.

what is cryptography?

all revoling around confidentiality, integrity,authenticity, and non-repudiation. Art and science of writing secrets.- Storing and transmitting information in a form that allows it to be revealed only to those intended.- Accomplished by cryptosystem.

non-repudation basically is

source cant say "wasnt me"

Asymmetric key cryptography is based on 'trap-door one way functions'

Public key: gives info about the function. - Private key: gives info about the trap door. - Whoever knows the trap door can compute function easily in both directions. - Anyone lacking trap door can only go easily in the forward direction.

digital signature: whose key do we use?

the private key of the sender to create the signature and the public key of the sender to verify it

digital signature: why do you need hashing algorithm?

to create a unique and fixed-length representation of the message. It provides integrity and authenticity by ensuring that even a small change in the message will result in a completely different hash value.

Symmetric key:

used to encrypt and decrypt it, both got the same copy of the key same on both sides,one key same for both partys.

Digital Signatures

• Authentication tool to verify a message origin and sender identity. - Resolve authentication issues. - Block of data attached to message (document, file, record, etc.). • Binds message to individual whose signature can be verified. - By receiver or third party. - Difficult to forge.

cryptology

- Includes both cryptography and cryptanalysis.

From a business perspective cryptography is about

- confidentiality -integrity -authenticity, -non-repudiation

All of the following are goals of physical security EXCEPT

Detain

The most important goal of any BCP is:

Preserve human life

Forward direction used for

encryption and signature verification

Business Continuity Plan (what do we do?)

establish the need for it, obtain management support, identify resources, and prepare an initial report

From a process perspective why is a BCP critical to support an organization?

provides a structured approach to identify and prioritize critical business functions, assess potential risks and vulnerabilities, and develop strategies to mitigate those risks

examples of corrective

robust backup mechanisms; they let you restore compromised data.

What is needed to make any cryptography breakable?

Time, timing of this is important from a business perspective. COST IS TIME

Digital Signatures Operation

To "sign" a message,* - Sender computes digest of message • Using public hash function - Crypto "signature" is made by sender's private key • Applied to digest creates digital signature - Digital signature sent along with message * - The message itself is not made private*

Cryptography Applications

-Prevent unauthorized disclosure of information -Detect Tampering

examples of preventative

badges, biometrics, key cards

Encipher/encrypt/encode

act of scrambling using key

Which of the following would be the best preventative control from a physical type?

( look at the examples and what would be best for preventative )

cryptanalysis

- Practice of defeating attempts to hide information.- Reduction or solution of secret messages without knowledge of the system or the key or the possession of a code book

what happens in recovery phase

- Respond to the Disaster - Recover Critical Functions - Recover Non-critical Functions - Salvage and Repair - Return to Primary Site

Algorithms

- Set of rules by which enciphering and deciphering is done.- 'Mathematical' function that takes plaintext and a key as input,and produces cipher text as output.• Cryptanalysis- Practice of defeating attempts to hide information.- Reduction or solution of secret messages without knowledge of the system or the key or the possession of a code book.• Cryptology- Includes both cryptography and cryptanalysis.

what happens in restoration phase

-Complete an assessment of all damage. -Initiate cleanup of the primary site. -Implement necessary replacement procedures.

Security requirements email example

-Privacy Only the intended recipient can read the message -Integrity The message cannot have been changed -Authentication We know the message is from who we expected it from - Non-repudiation Originator cannot deny having sent a message

Strengths of Symmetric Key Cryptography

-Very fast, large amounts of data in little of time -Very difficult to break data encrypted with large keys -Availability- algorithms and tools used for symmetric encryption are freely available, this lets business rely on it

Which of the following examples would best fit the "Deter" goal of physical security?

A sign on a fence that reads "WARNING: electrified fence" that is installed around the HVAC system on the side of a building

What is the initial requirement to be preformed in establishing a business continuity plan?

Agree on the scope of the plan

Digital Signatures (cont.) -

Each user has public-private key pair • Private key signs (creates signature), public key verifies it. - A digital signature is created by encrypting a digest or hash value of a message with the senders private key

DES-Data Encryption Standard

Block mode cipher 64-bit input and output size 56 - bit true key plus 8 parity bits -72 quadrillion possible keys 16 rounds of transportation and substitution to encrypt and decrypt

DES ( cont)

Cryptanalysis assumptions- Algorithm is known by the adversary. The strength of the encryption relies on the secrecy of the key(Kerckhoff's Principle).- Adversary must try all possible keys to find which one was used.

Asymmetric Key Cryptography (cont.) Strengths

Can provide five security elements: • Confidentiality/Privacy (Data cannot be decrypted without the appropriate private key) • Access Control (The private key should be limited to one person) • Authentication (Identity of sender is confirmed) • Integrity (Data has not been tampered with) • Non-repudiation (Sender cannot deny sending)

Digital signatures do not allow for?

Confidentially of the message

Which is the best know example of a symmetric key cipher?

DES

Digital Signatures Scheme

DSS (Digital Signature Standard)- every digital signature is built on this.

Decipher/Decrypt/Decode

Descrambling with key

A camera located outside a server room door supports which of the following physical security objectives

Detect

Goals of Physical Security

Deter, Delay, Detect, Assess, Respond

Using asymmetric(public key) encryption to provide the recipient of a message with " proof of Origin" requires that the sender

Encrypt the message with the senders Private Key

A stream mode cipher would be most applicable for which of the following task?

Encrypting a real-time broadcast of a digital video conference between heads of state

Stream and block ciphers: when is it appropriate to use either one, what type of communication.

For stream, live tv, real time zoom call For block, much better for data that asynchronous does not really need to be there in a timely matter. Large data dumps might occur 1 or twice a day. Question: which one would you use in this scanioro , what one is appropriate for the type of business engaging in

Which of the following best describes a hot site:

Fully equipped back up center with external interfaces (power,water,etc) and telecommunications as well as complete computing resources on site.

Hash Function (cont.) -

Hash functions should be one-way (messages cannot be generated from their signature) - It should be computationally infeasible to compute the same hash value on two different messages - Should resist birthday attacks

Weaknesses of Symmetric Key Cryptography

Key management and implementation - Ensure that sender and receiver can agree upon a key, and how they exchange a key. • Key Distribution- Same key used to both encrypt and decrypt.- Requires very secure mechanism for key distribution.- Keys and data must be delivered separately. Scalability- Since a unique symmetric key must be used between the sender and each recipient, number of keys grows exponentially with the number of users : N (N-1) / 2• 10 users = 45 keys• 1000 users = 499,500 keys Limited security- Symmetric keys only encrypt data and restrict its access.- Does not provide proof of origin or non-repudiation.

Which of the follow is NOT a key strategy for developing a physical security program

Management support for physical measurements of security

in order of least allowable downtime to most allowable downtime , rank these recovery strategies

Mirror Site, Hot Site, Warm Site, Cold Site

Examples of types of physical access controls include all of the following except :

Passwords

Asymmetric- Every person as two keys

Private key Public key 'key pair' the two keys have a relationship between each other

What is a hash function?

Used to condense arbitrary length messages and produce fixed-size representation of message. • Used for subsequent signature by a digital signature algorithm

question that could be asked: for physical security what would be an example of this?

Video surveillance, security guards, protective barriers, locks, and other systems designed to protect persons and property

plaintext/cleartext

data in unscrambled form

Inverse direction used for

decryption and signature generation

Business Continuity Plan (how/why do we use it?)

enables an organization to ensure safety, minimize loss, facilitate recovery, and repair or replace damaged facilities in the event of disruptions to normal business operations

private key

kept secret and known only to the owner

digital signature: what does it provide for you?

non-repudiation, meaning the sender cannot deny sending the message, and it verifies the message's origin and sender identity.

Layers of defense

organizational safeguards in place to prevent anticipated injury, damage, or failure

Asymmetric Key Cryptography Strengths

• Provides efficient encryption and digital signature services • Efficient symmetric key distribution • Scalability - Only two keys needed per user • 1,000 people need total of 2,000 keys (easier to manage than the 499,500 needed for symmetric)

Digital Signatures Benefits

• Provides non-repudiation. - Ensures that the sender cannot deny sending the message. - Recipient cannot claim receiving a different message than the original. • Used to authenticate software, data, images, users, machines. - Protects software against viruses. - A smart card with a digital signature can verify a user to a computer.

Digital Signatures Operation (cont.)

• To verify a message ** - Receiver computes digest of received message - Decrypts the signature with the sender's public key to extract the original sender's digest - Verifies if the recomputed and decrypted digests match • Signature decryption identifies sender and verifies integrity of the message