7) Principles of Security?
a) The main principles of security ensure that data and
systems are protected from unauthorized access, misuse, or
attacks.
They include:
1) Confidentiality:
Ensures that only authorized users can access
sensitive information.
Example: When A sends a $100 check to B, only B
should be able to see its contents.
2) Integrity:
Protects data from being tampered with. A and B
must ensure the check's amount, date, or signature isn’t
altered during transit. This is the principles of integrity.
3) Authentication:
Confirms the identity of users. B must verify the
check is truly from A, not someone pretending to be A.
This the principles of authentication.
4) Non-repudiation:
Prevents denial of actions. A cannot later deny
sending the check because A’s signature proves the action.
5) Access-Control:
Defines who can access or modify data. For
example, user A may only view a database, while user B
can update it.
Access Control is broadly related to two areas
a) Role Management- Concentrate on the user side.
b) Rule Management- It focuses on the resources side
6) Availability:
Ensures systems and data are accessible to
authorized users when needed.
For example, a denial-of-service (DoS) attack can
violate this.
7) Ethical&Legal-Issues:
Involves respecting user privacy and complying
with laws. There’s a balance between individual rights and
the greater good of society.
Example: Company, Society
8) Explain in detail about?
1) symmetric key cryptography 2) Asymmetric key cryptography
1) Symmetric Key Cryptography:
o In symmetric key cryptography, the same key is used for
both encryption and decryption.
o It is also called secret-key cryptography because the key
must be kept secret between sender and receiver.
o The sender uses the key to encrypt the message, and the
receiver uses the same key to decrypt it.
o It is fast and suitable for encrypting large amounts of data.
o A major challenge is secure key sharing, as both parties
must have access to the same secret key.
Features:
• Speed: Very fast and suitable for real-time communication.
• Simplicity: Uses only one key.
• Security depends on key secrecy.
Example: AES (Advanced Encryption Standard)
DES (Data Encryption Standard)
2) Asymmetric Key Cryptography:
o In asymmetric key cryptography, two keys are used: a public
key and a private key.
o The public key is shared with everyone, while the private
key is kept secret by the owner.
o If a message is encrypted with the public key, it can only be
decrypted with the corresponding private key, and vice
versa.
o This method is more secure for communication, but slower
than symmetric cryptography.
o It also provides digital signatures and authentication.
Features:
• Key Pair: Public key (shared), Private key (kept secret).
• Secure Key Exchange: No need to share secret keys.
• Supports Digital Signatures.
Example: RSA (Rivest–Shamir–Adleman)
ECC (Elliptic Curve Cryptography)
10) Explain RSA algorithm with a neat diagram?
a)
RSA (Rivest-Shamir-Adleman) Algorithm:
RSA is a widely used asymmetric key cryptographic algorithm
that uses a pair of keys: a public key for encryption and a private key
for decryption. It is based on the mathematical difficulty of factoring
large prime numbers.
Steps in RSA Algorithm:
1. Key Generation:
• Choose two large prime numbers: p and q
• Compute n = p × q
• Compute Euler’s totient: φ(n) = (p-1)(q-1)
• Choose e such that 1 < e < φ(n) and gcd (e, φ(n)) = 1
• Compute d such that (d × e) mod φ(n) = 1
• Public Key: (e, n)
• Private Key: (d, n)
2. Encryption:
• Sender uses recipient’s public key (e, n)
• Plaintext message M is encrypted as:
C = M^e mod n
3. Decryption:
• Receiver uses their private key (d, n)
• Ciphertext C is decrypted as:
M = C^d mod n
Example:
Let p = 61, q = 53
• n = 61 × 53 = 3233
• φ(n) = 60 × 52 = 3120
• Choose e = 17, then d = 2753
• Public key: (17, 3233)
• Private key: (2753, 3233)
Encrypt message
M = 72 (H):
• C = 72^17 mod 3233 = 2103
Decrypt message:
• M = 2103^2753 mod 3233 = 72 → H
Applications of RSA:
• Secure key exchange
• Digital signatures and certificates
• HTTPS / SSL (web encryption)
• Secure email and VPNs
11) DIFFI HELLMAN key exchange algorithm example?
a)
Diffie-Hellman is a key exchange algorithm used to
securely share a secret key between two people over a public
network.
It allows both users to generate a common key used for
encryption, even if an attacker is listening.
Steps:
1) Two people, Alice and Bob, agree on two public numbers:
o A prime number p
o A base g (called generator)
2) Alice chooses a private number a and calculates:
A = (g^a) mod p and sends A to Bob.
3) Bob chooses a private number b and calculates:
B = (g^b) mod p and sends B to Alice.
4) Now both calculate the shared secret key:
o Alice: S = (B^a) mod p
o Bob: S = (A^b) mod p
Both get the same key S, without sending it directly!
Example:
Let:
• p = 23 (a prime)
• g = 5 (a primitive root of 23)
Step 1: Private Keys
• Alice chooses a = 6
• Bob chooses b = 15
Step 2: Public Keys
• Alice computes A = 5^6 mod 23 = 15625 mod 23 = 8
• Bob computes B = 5^15 mod 23 = 30517578125 mod 23
=2
Step 3: Exchange Public Keys
• Alice sends 8 to Bob
• Bob sends 2 to Alice
Step 4: Shared Secret
• Alice computes S = 2^6 mod 23 = 64 mod 23 = 18
• Bob computes S = 8^15 mod 23 = 18
Both got the same secret key: 18
Applications:
• Used in SSL/TLS (web security)
• VPNs
• Secure messaging (e.g., WhatsApp)
