Network Security 1
Network Security 1
Encryption
- = process of encoding a message in such a way that only authorised parties can access it
- Sender: uses a secret key & an encryption algorithm to encrypt a plaintext to a cipher text message
- Receiver: uses a secret key & a decryption algorithm to decrypt the cipher text to the original plaintext message
- The Internet: Encryption & Public Keys
[1] Symmetric Encryption
- 1 key shared between sender & receiver
- Same encryption & decryption key
- Fast processing
- Low security once key was intercepted
- E.g. Advanced Encryption Standard (AES)
[2] Asymmetric Encryption
- 1 public key & 1 private key that are mathematically related
- 1 cannot be derived from another
- Slower than symmetric encryption but more secured
- Sender uses receiver’s public key to encrypt the message
- This public key can be shared with anyone
- Receiver’s private key is the only key to decrypt the message
- Even if public key is incepted, the message is still kept secret
- E.g. Rivest-Sharmir-Adleman (RSA)
Digital Signature
- Electronic signature: equivalent to paper signature, an electronic record adopted by a person with the intent to sign a contract
- Digital signature: the encryption & decryption technology that secures the data associated with a signed document and helps verify the authenticity of the document
- Purpose
- Authentication: message was created by the known sender
- Non-repudiation: sender cannot deny having sent the message
- Integrity: the message is not altered in transit
- Widely used on Internet, emails, and block chains
- Technology involved in Digital Signature
- Note: message may not be encrypted
- Encryption (use of private & public key)
- Hashing
- Generating a short string of text (hash / hash value / digest) from any size of data
- Unique hash for different data
- Impossible to recover original data from the hash
- Provides confidentially / integrity
- E.g. SHA256 (Secure Hash Algorithm)
- Sender side
- Sender uses a hash algorithm to create a hashed version of the message
- Sender uses its private key to encrypt the hash to the digital signature
- Both message (encrypted or not) & digital signature are sent to received
- Receiver side
- Receiver uses sender’s private key to decrypt the digital signature back to the sender’s version of hash
- Receiver uses same hash algorithm to create a new hash from the received message
- If the 2 hashes match, means data is not altered and is sent by the known sender
| Identification | User claims an identify | E.g. ISP username |
|---|---|---|
| Authentication | System validates identity of a user | E.g. ISP username + password |
| Authorisation | System validates the granted permission of an authenticated user to access the resources | E.g. different ISP modules for students & staff |
Authentication
- Users to prove their identity by providing some type of credentials
- Authentication Factors
- Something you know: e.g. security question, password
- Something you have: e.g. staff card, NRIC
- Something you are: fingerprint / facial recognition
- Multi-Factor Authentication (MFA)
- Combination of at least 2 factors of authentication
- E.g. password + staff card; password + fingerprint