CCNA Security

1. RSA Algorithm
For CCNA Security - Simplified
Overview
Mohamed Mahmoud Ibrahim

2. 🔐 What is RSA Algorithm?
• RSA stands for Rivest–Shamir–Adleman.
• It's an Asymmetric Encryption algorithm used
for secure data exchange, digital signatures,
and authentication.

3. 💡 RSA Basic Idea
• RSA uses two keys:
• - Public Key : Used for encryption or
🔓
signature verification.
• - Private Key : Used for decryption or
🔒
creating a signature.
• It relies on the difficulty of factoring large
prime numbers.

4. ⚙️How RSA Works - Steps
• Key Generation
1 ️
1️⃣
• Encryption using Public Key
2️⃣
• Decryption using Private Key
3 ️
3️⃣
• Based on modular arithmetic and prime
factorization.

5. 🧠 RSA - Key Generation
• 1. Select two large prime numbers: p and q
• 2. Compute n = p * q
• 3. Compute φ(n) = (p-1)*(q-1)
• 4. Choose e (1 < e < φ(n), and e is coprime to
φ(n))
• 5. Calculate d so that (d * e) % φ(n) = 1
• Public Key = (n, e)
• Private Key = (n, d)

6. 🔐 Encryption Process
• 1. Convert the plain message into a number
(M).
• 2. Apply the formula:
• Cipher Text (C) = (M ^ e) % n
• 3. Send the encrypted message C to the
recipient.
• Only the recipient's private key can decrypt it.

7. 🔓 Decryption Process
• 1. Receive the Cipher Text (C).
• 2. Apply the formula:
• Original Message (M) = (C ^ d) % n
• 3. This restores the original plain message.
• Only the private key holder can decrypt the
message!

8. 🎯 RSA Example - Key Generation
• Given:
• p = 7, q = 11
• n = p * q = 7 * 11 = 77
• φ(n) = (p-1)*(q-1) = 6 * 10 = 60
• Choose e = 17 (Coprime with 60).
• Find d: (d * 17) % 60 = 1 → d = 53.
• Public Key: (77, 17)
• Private Key: (77, 53)

9. 🎯 RSA Example - Encrypt & Decrypt
• Original Message (M) = 10
• Encryption:
• C = (10 ^ 17) % 77 = 10 (simplified)
• Decryption:
• M = (10 ^ 53) % 77 = 10
• ✅ Message recovered successfully!

10. 💼 RSA in CCNA Security
• - VPN Security: Safe Key Exchange
• - SSL/TLS: Secures Web Communication
• - Digital Signatures: Authentication & Integrity
• - Digital Certificates: Identity Verification (PKI)

11. ✅ Final Summary
• RSA is a Public Key Cryptography system.
• Used for securing communications, digital
signatures, and certificates.
• Essential for understanding CCNA Security
topics like VPN, HTTPS, and PKI.
• ⚡️Efficient, reliable, and foundational in
network security.