1. Definitions
Non-Repudiation:
Non-repudiation is a security principle that ensures a sender cannot deny having sent a message and a receiver cannot deny having received it. It provides proof of origin, delivery, and integrity of data, preventing either party from denying their actions in a communication.
Authentication:
Authentication is the process of verifying the identity of a user, system, or entity before allowing access to a system or data. It ensures that the entity is who it claims to be.
2. How Non-Repudiation and Authentication are Achieved
Both can be achieved using digital signatures and public key cryptography.
Mechanism:
| Technique | Purpose |
|---|---|
| Digital Signature | Provides non-repudiation |
| Public Key Encryption | Provides authentication and confidentiality |
3. Example Using Public Key Infrastructure (PKI)
Let’s consider two parties: Alice (Sender) and Bob (Receiver).
Step-by-Step Process:
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Authentication:
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Bob wants to ensure that the message he received is truly from Alice.
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Alice digitally signs the message using her private key.
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Bob uses Alice’s public key to verify the signature.
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If verification succeeds, it confirms Alice’s identity (Authentication).
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Non-Repudiation:
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Since only Alice has access to her private key, she cannot deny having sent the message.
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The signature acts as evidence in case of a dispute.
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4. Example in Practice (Pseudocode):
// Alice signs the message
Message = "Project submitted"
Signature = Sign(Message, Alice_PrivateKey)
// Alice sends (Message + Signature) to Bob
// Bob verifies
IsValid = Verify(Message, Signature, Alice_PublicKey)
If IsValid:
Print("Message is authentic and non-repudiable")
Else:
Print("Message verification failed")5. Conclusion
Non-repudiation ensures that senders cannot deny their messages, while authentication ensures that entities are correctly identified. These security objectives are crucial in digital communications and are effectively achieved through cryptographic techniques like digital signatures and public key cryptography.