Security Services and SEO

What is encryption?

Converting readable data into ciphertext to prevent unauthorised access.

What is a cryptographic key?

Digital information used by an algorithm encryption or decryption

What is symmetric encryption

Encryption that uses the same shared secret key to encrypt and decrypt data.

What is asymmetric encryption

Encryption that uses a mathematically linked key pair(public and private key) to encrypt and decrypt data.

How does public-key encryption provide confidentiality?

The sender encrypts the data using the receivers public key and the receiver decrypts the data using their private key. This prevents unauthorised users from intercepting the data.

What is a disadvantage of symmetric encryption?

The secret key must be shared securely between the sender and receiver, or else unauthorised users may access it and hence be able to decrypt the data.

What is SSL, and what replaced it?

Secure Sockets Layer is a protocol that protects data transmitted across a network.

It is obsolete and has been replaced by Transport Layer security

What three security services does TLS provide?

Confidentiality

Integrity

Authentication

How does TLS provide confidentiality?

It encrypts transmitted data to prevent unauthorised people from reading it.

How does TLS ensure integrity?

Cryptographic checks help detect unauthorised changes to transmitted data.

How does TLS help authenticate a website?

It uses digital certificates and cryptographic checks to help verify a websites identity.

Why does TLS use symmetric encryption to protect large amounts of data?

Symmetric encryption is generally faster and more efficient than public-key encryption for bulk data

What is a digital certificate?

An electronic document that links a public key to the identity of a person, organisation or website

What is a certificate authority (CA)

A trusted organisation that issues and digitally signs digital certificates.

What does a browser check when verifying a digital certificate?

The trust chain

Validity period

Domain-name match

Revocation status where checked

Does a digital certificate itself encrypt transmitted data?

No. It helps establish trust in a websites identity + public key.

What is a digital signature used for?

It helps verify who signed the data and whether it has been altered.

What is a digital signature?

A cryptographic mechanism that uses a private key to sign DATA and a public key to verify it, to ensure authenticity and integrity of digital documents and messages.

Why might a browser warn a user that a websites certificate has expired?

The certificate is outside the validity period, so the browser cannot rely on it normally to establish trust?

What is a ledger?

A record of transactions

What is a transaction in digital currency?

A record of a transfer of digital currency between addresses.

What is a distributed database?

A database whose data is stored or maintained across multiple computers.

What is decentralisation?

Control is distributed among participants instead of being held by one central authority.

What is a blockchain?

A type of DISTRIBUTED LEDGER that records transactions in blocks linked by cryptographic hashes.

What is a cryptographic hash?

A fixed length value calculated from data. Changes to the data normally result in a different hash.

What is a node in a blockchain network?

A computer participating in the network by maintaining or validating blockchain data(data on a blockchain network).

What is double-spending?

Attempting to spend the SAME digital currency more than once.

How does blockchain help detect tampering?

Changing a block changes its cryptographic hash, causing the HASH LINK to the NEXT BLOCK AND subsequent blocks to mismatch (be invalid).

How does blockchain help prevent double spending?

Transactions are checked against the ledger and network consensus rules, which help reject conflicting transactions.

What is the difference between a distributed database and a decentralised system?

Distributed refers to where the data is maintained; decentralised refers to how control is shared.

Why is changing an old blockchain transaction difficult?

Changing a block:

1. Alters its hash

2. Breaks the links to later blocks

3. Requires overcoming the network’s consensus protection

What is search engine optimisation?

The process of improving a website so that it ranks higher in the organic(unpaid) search results of a search engine.