Non-repudiation - 1.2

Proof of Integrity

Hashing is used to create a "fingerprint" of a file or data. This fingerprint (or hash) can be stored or transmitted alongside the original data and later compared to verify whether the data has been altered.

Even a small change in the content will produce a significantly different hash, making it easy to detect tampering or modifications.

Proof of Origin

Proof of origin ensures that the data or message comes from a claimed, authenticated source.

A private key is used by the sender to digitally sign the data. The recipient can use the corresponding public key to verify the signature, ensuring that the message came from the legitimate sender and has not been altered.

Ensuring the signature is genuine is crucial for non-repudiation:

• Repudiation: The act of denying an action or event, such as sending a message or signing a document.
• Non-repudiation: Ensures that a sender cannot deny having sent a message or performed an action. This provides both proof of the origin of the message and ensures its integrity.

Hashing Algorithms

How do hashing algorithms work?

Hashing algorithms take input data of any size and generate a fixed-length, unique string of characters (hash value). This hash value is unique to the input data, meaning even a slight change in the original data results in a completely different hash value. This property helps ensure data integrity.

Common hashing algorithms include:

• SHA-256: A secure hashing algorithm commonly used for security applications, producing a 256-bit hash value.
• MD5: An older hashing algorithm that generates a 128-bit hash value, but is now considered less secure due to vulnerabilities discovered over time.