Cryptography is the science of using mathematical techniques to secure communications. It directly involves modifying messages through processes like encryption (to ensure confidentiality) and hashing (to ensure integrity). By transforming plaintext into ciphertext, cryptography protects message content from unauthorized access (hacking) during transmission over insecure networks like the Internet. It is the fundamental technique used to provide core information security services such as confidentiality, integrity, authentication, and non-repudiation for data in transit, thereby reducing the risk of various cyber attacks.

A. Risk analysis: This is a management process to identify and evaluate risks to assets; it does not technically modify messages or act as a direct communication security control.
B. OODA loop: This is a strategic decision-making model (Observe, Orient, Decide, Act) used for responding to incidents, not a technical method for securing message content.
D. Firewall security: A firewall is a network device that filters traffic based on rules to control access. It does not modify the content of messages for confidentiality or integrity.

1. National Institute of Standards and Technology (NIST). (2020). Special Publication (SP) 800-57 Part 1 Rev. 5: Recommendation for Key Management.

Section 2.1

Page 5: "Cryptography is the science of using mathematics to hide data. It provides mechanisms that underlie many of the security services

including confidentiality

data integrity

authentication

and non-repudiation." This directly supports cryptography as the technique for providing security services by modifying data.

2. Stallings

W. (2017). Cryptography and Network Security: Principles and Practice (7th ed.). Pearson.

Chapter 1

Section 1.1

Page 3: The text defines the objectives of cryptography in providing security services for information in transit. It states

"The two fundamental security services provided by cryptography are confidentiality (using encryption) and data integrity (using message authentication codes or digital signatures)."

3. Pfleeger

C. P.

Pfleeger

S. L.

& Margulies

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

Chapter 12

Section 12.1

Page 668: "Cryptography is the study of encryption and decryption... It is the art of devising ciphers... to protect the confidentiality and integrity of data." This confirms cryptography's role in modifying messages to provide security.