Question

Confidentiality, integrity, availability, authentication, and nonrepudiation are fundamental security properties. For each of these properties, explain if it can be provided by public-key cryptography. If yes, explain how.

Short answer

Public-key cryptography supports confidentiality, integrity, authentication, and nonrepudiation, but not directly availability.

Step-by-step solution

Understanding Confidentiality

Confidentiality ensures that information is accessible only to those authorized to have access. Public-key cryptography provides confidentiality through encryption: a sender encrypts the data using the recipient's public key, and only the recipient can decrypt it using their private key.

Exploring Integrity

Integrity guarantees that data is not altered or tampered with. Public-key cryptography supports integrity with digital signatures, allowing a sender to sign data with their private key. The recipient can verify this signature using the sender's public key, ensuring the data hasn't changed.

Examining Availability

Availability ensures that systems and data are accessible to authorized users when needed. Public-key cryptography does not directly address availability, but it can support systems that enhance availability, such as secure key management and communications, indirectly contributing to system stability and scaling.

Authenticating Users (Authentication)

Authentication confirms the identity of users. Public-key cryptography provides authentication by using digital signatures. During an interaction, one party can verify the other's identity by checking a digital signature against a known public key.

Understanding Nonrepudiation

Nonrepudiation prevents an entity from denying its involvement in a transaction. Public-key cryptography provides nonrepudiation through digital signatures, as a signature created with a private key can be verified by others with the corresponding public key, assuring the signer's identity and intent.

Key concepts

Confidentiality

Confidentiality in digital communication ensures that sensitive information is not accessible to unauthorized individuals. Public-key cryptography plays a crucial role in maintaining confidentiality by employing encryption techniques. In this system, data is encrypted using the recipient's public key. This means that only the person with the corresponding private key can decrypt and access the data. It's like sending a letter in a sealed envelope that only the intended recipient can open. Thus, confidentiality helps to protect information from prying eyes, ensuring that only those with permission can view the data.

Integrity

Integrity is all about ensuring that the data remains unchanged from its original form. Public-key cryptography tackles this with the help of digital signatures. A digital signature is created when a sender encrypts data with their private key. When the recipient receives this data, they can use the sender's public key to verify the signature. If the signature matches, it guarantees that the data has not been altered during transit. This way, integrity provides assurance that the data sent is the same as the data received, without any alterations.

Authentication

Authentication is the process of verifying the identity of a user or entity. Public-key cryptography enables authentication through digital signatures. When two parties engage in communication, each can confirm the other's identity by checking a digital signature against a known public key. Think of it as a way to prove you are who you say you are, just like presenting a driver's license. It ensures trust between parties, allowing them to interact securely, knowing they are communicating with legitimate entities.

Nonrepudiation

Nonrepudiation is about ensuring that once a party has been involved in a transaction, they cannot deny their participation. For this, public-key cryptography utilizes digital signatures. When someone signs a document or message with their private key, they are creating a unique signature. This signature can be independently verified using the corresponding public key by others. Therefore, it holds the signer accountable, as it proves their involvement and intent, making it impossible to later claim that the action didn't occur.