Purpose Key Cryptography
- Ensures a message is authentic/ from a trusted source
- Ensure message has not been altered during transmission
- Makes sure only the intended receiver is able to understand a message
Asymmetric Encryption - Explain (4 - 5 marks)
- Provides better security by using a pair of different key
- One of the keys is used to encrypt the message, the matching one is used to decrypt it
- Only the public key is available to everyone, private key is kept secret (hence the name)
- Is a longer process, as it is more complex
- Length of key is longer -> Usually 2048
Process of communication using Asymmetric Encryption
- The receiver’s computer uses an algorithm to generate a matching pair of keys
- The public key is sent to the sender’s computer
- ## The sender encrypts the document/ file/ data using the key to create cipher text
How will the sender/ receiver realise that their massage has been altered? (4 marks)
- The message and the digital signature is decrypted using the receiver’s private key
- The digital signature received is decrypted with the sender’s public key to recover the digest sent
- The decrypted message received is hashed with the agreed hashing algorithm to reproduce the message received
- The two digests (received ad reproduced) are compared
What is Symmetric Encryption
Symmetric Encryption
- Uses a single key which is used/ shared by all to encrypt and decrypt messages
- Simple process that can be carried out quickly, higher risk of compromise
- Shorter key length when compared to asymmetric encryption
What is Quantum Cryptography
- Encryption that uses photons and filters
- Protects security of data transmitted over fibre optic cable
- Virtually unhackable encryption system
2 Advantages and Disadvantages of Quantum Cryptography
Advantages
- Detects any Eavesdropping from the change of photons
- Once transferred, the integrity of the key can be guaranteed: It cannot be copied nor decrypted later
- More secure, longer keys are used
Disadvantages
- Expensive
- Limited Range
- Polarization of light may be altered during the transmission through the fibre optic cable
- Its new: Still lack vital features and has high error rate
What is a Private Key
- As the name suggests, its a secret key that is never transmitted
- It has a matching public key
Is used to decrypt date that was encrypted with its matching public key.
SSL/ TLS use when Client - Server Communication is Initiated
SSL/ TLS Connection is initiated by an application which becomes the client
- Application which receives the connection becomes the server
Every new session begins with a handshake
- A digital certificate is requested from the client
- The requested certificate is then sent by the server
- The client verifies the server’s digital certificate and obtain the server’s public key
- Encryption algorithm are agreed upon by the client and server
Key pair is generated
How are Digital Signatures acquired
- An enquiry is made to Certificate Authority (CA)
- The enquirer sends their public key and all required information to CA
- The enquirer’s details are checked by the CA -> If details are verified then the public is agreed upon
- The CA creates/ issues a certificate that includes the enquirer’s public key
- Encryption data is sent to the CA using their public key and sent by the CA using their private key
How is a Digital Signature produced before a message is sent?
- Message is hashed using the agreed hashing algorithm to produce a digest
- The message digest is then encrypted with the sender’s private key to form the signature
What is a Digital Certificate
Its an:
- Electronic/ Online document used to authenticate the identity of a website/ individual/ organisation
- Typically issued by the CA
- Contains information for identifying an individual/ website owner as well as a public key
Role of Certificate Authority in creating a Digital Signature
- They provide the public key which can be used to validate the private key associated with the signature
