Danni-Tech

Welcome to my complete CompTIA Security Plus course. This is Danny Tech! This course aims to be a complete course for Security Plus 100% free stay tuned until the end as there will be a quiz to test your knowledge of the material in this video now let’s get started.

Non- Repudiation, ensuring accountability in cryptography.

Non-repudiation is a critical concept in cryptography that ensures a sender cannot deny sending information. However, it does not guarantee that the receiver cannot deny receiving it. Additional mechanisms, such as a signed acknowledgments or third-party verification, are needed to ensure the receiver’s accountability.

Now, Non reputation  is achieved through proof of origin (verifying who sent the data) and proof of integrity (ensuring the data hasn’t been altered). Think of it as the digital equivalent of signing a contract—you can’t later claim you didn’t sign it if your signature is on the document.

Proof of Integrity

Integrity ensures that the data received is exactly the same as the data sent, with no changes made along the way. In cryptography, this is achieved using a hash.

A hash is like a unique fingerprint for data. If even one character of the data changes, the hash value will change completely. This makes it easy to detect if the data has been tampered with. 

For example:

Let’s say that John is sharing an important document with Susie. Before sending it, John uses a hashing algorithm to create a hash value for the document. He sends both the document and the hash to Susie. When Susie receives the document, she runs the same hashing algorithm on it. If her hash matches the one John sent, she knows the document hasn’t been altered. If the hash doesn’t match, Susie can immediately tell something went wrong—either the data was corrupted during transmission or tampered with.

Now While a hash can confirm that the data hasn’t been changed, it doesn’t tell us who sent it. This is where digital signatures come in. A digital signature not only verifies the integrity of the data but also confirms the identity of the sender.

Let’s see how this works with John and Susie:

John wants to send a message to Susie that says, “Let’s meet at 2 PM.” Before sending it, John creates a hash of the message using a hashing algorithm. Then, he uses his private key to encrypt the hash. This encrypted hash becomes the digital signature.

John sends Susie two things:

• The original plaintext message (“Let’s meet at 2 PM”).
• The digital signature (the encrypted hash).

When Susie receives the message, she uses John’s public key to decrypt the digital signature. This gives her the original hash that John created. Next, Susie runs the same hashing algorithm on the plaintext message she received. She compares the hash she generates with the hash from the digital signature.

If the hashes match, Susie knows two things:

• The message hasn’t been altered (proof of integrity).
• The message was sent by John, because only John’s private key could have created the signature (proof of origin).

This entire process happens seamlessly, often with just a click of a button to “sign” or “verify” the message. 

Non-repudiation is vital for secure transactions, such as signing legal documents, sending sensitive emails, or verifying software updates. It ensures accountability and builds trust by confirming both the authenticity of the sender and the integrity of the data.

For example, if John sends Susie an important contract digitally signed with his private key, Susie can verify that it’s really from John and that no changes were made. Likewise, John can’t deny sending it later, because the signature is tied exclusively to his private key.