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Non-Repudiation

Non-repudiation ensures that individuals or entities involved in a communication or transaction cannot deny their participation or the authenticity of their actions. Provides undeniable proof of involvement, similar to a signed receipt for a letter.

Importance and Historical Context

  • Non-repudiation has a long history, from kings using unique signet rings for document authenticity to digital methods today.
  • In digital security, non-repudiation is achieved with digital signatures, offering assurance that a message or transaction:
    • Originated from a stated source
    • Remains unaltered throughout transit

Digital Signatures and Non-Repudiation

  • Digital Signature Process:
    1. The message is hashed.
    2. This hash digest is encrypted with the sender’s private key using asymmetric encryption.
    3. The resulting digital signature verifies authenticity and ensures the message has not been altered.
  • Unique to Each User: Only the sender's private key can create a valid signature, which prevents others from impersonating them.

Key Benefits

  1. Confirming Authenticity

    • Ensures that digital transactions or communications genuinely come from the claimed source.
    • Example: A digitally signed email from a person can’t be denied as their own, whereas an unsigned email offers no authenticity guarantee.

  2. Ensuring Integrity

    • Digital signatures help confirm that data hasn't been tampered with, as any modification breaks the signature.
    • This relies on hash values in the digital signature, maintaining both non-repudiation and integrity.

  3. Providing Accountability

    • Users are aware their actions are traceable, fostering responsibility.
    • Example: Auto insurance companies use driving apps that require smartphone authentication, collecting data and establishing non-repudiation by linking driving habits to the individual.