Which of the following is always true regarding the use of encryption algorithms based on public key infrastructure (PKI)?

The core function of authentication within a Public Key Infrastructure (PKI) relies on the principle of asymmetric cryptography. Each party possesses a key pair: a public key, which is widely distributed, and a private key, which is kept secret and is unique to that party. To authenticate themselves, a party uses their private key to perform a cryptographic operation, such as creating a digital signature. Because only that party has access to the private key, a successful verification of the signature using the corresponding public key proves the identity of the sender, thus uniquely authenticating them for that transaction.

A. A PKI can be managed by an internal Certificate Authority (CA) within a single organization, meaning the administrator is not always independent.
B. In a private or enterprise PKI, the Certificate Authority that authenticates the public key is part of the same organization, not a "third party."
C. While PKI is a critical enabler for e-commerce, it is also used for many other purposes, such as secure email (S/MIME), code signing, and VPN authentication.

1. National Institute of Standards and Technology (NIST)

Special Publication 800-32

"Introduction to Public Key Technology and the Federal PKI Infrastructure."

Section 2.1.2

"Digital Signatures

" states: "The digital signature provides... Authentication: Since the private key is held by a single user

the digital signature authenticates that user as the originator of the message." This directly supports the role of the private key in unique authentication.

2. Pfleeger

C. P.

Pfleeger

S. L.

& Margulies

J. (2015). Security in Computing (5th ed.). Prentice Hall.

Chapter 5

"Cryptography

" Section 5.4

"Public Key Encryption

" explains that a message signed with a user's private key authenticates the origin of that message

as only the legitimate user has access to that key. This principle is foundational to PKI.

3. MIT OpenCourseWare

6.857 Computer and Network Security

Fall 2017.

Lecture 7 Notes

"Public-Key Cryptography

" details how digital signatures work. It specifies that a signature σ = Sign(SK

m) is created using the secret key (private key) SK. The verification function Vrfy(PK

m

σ) uses the public key PK. A successful verification authenticates that the message m was signed by the owner of SK.