Hashing and Digital Signatures & Blockchain technology- CompTIA Security+ SY0-701 - 1.4.6 - 1.4.7

Hashes

Represent data as a short string of text (a message digest)

• Impossible to recover the original message from the digest

• Used to store passwords and provide confidentiality

• Can be a digital signature for authentication,

non-repudiation, and integrity

• A well designed hash will not collide

• Different messages will not have the same hash

SHA256 Hash

256 bits.

64 hexadecimal characters

Collision (hashing)

Hash functions

- Take an input of any size

- Create a fixed size string

- Message digest, checksum

The hash should be unique

- Different inputs should never create the same hash, otherwise its a collision

MD5 has a collision problem

- Found in 2996

- Don't use MD5 for anything important

Practical hashing

Verify a downloaded file

-Hashes may be provided on the download site

-Compare the downloaded file hash with the posted hash value

-Password storage

-Instead of storing the password, store the hash

-Compare hashes during the authentication process

-Nobody ever knows your actual password

Salt

Random data added to a password when hashing

Every User gets their own random salt

- salt is commonly stored with the password

Rainbow tables wont work with salted hashes

- Additional random value added to the original password

Slows things down during brute force process

- But doesn't completely stop reverse engineering

Digital Signature

an encrypted code that a person, website, or organization attaches to an electronic message to verify the identity of the message sender

Provides the following

- Integrity

- Authentication

- Non repudiation

Signed with a private key and any change invalidates the signature

Blockchain

A distributed and decentralized ledger that records and verifies transactions and ownership, making it difficult to tamper with or shut down.

Practical application of blockchain includes

- Payment processing

- Digital identification

- Supply chain monitoring

- Digital voting

Blockchain process

1. Initiate Transaction

2. Validate Transaction

3. Create a Block

4. Calculate and insert a hash

5. Complete transaction