Asymmetrical encryption, also known as public-key cryptography, utilizes a pair of mathematically related keys: a public key and a private key. The public key is distributed freely and is used to encrypt data, while the corresponding private key is kept secret and is the only key capable of decrypting that data. This one-way process, where one key encrypts and the other decrypts, is the defining characteristic of this encryption type and is fundamental to securing communications over public networks.

A. Symmetrical encryption: This method uses a single, identical key for both the encryption and decryption processes, which must be shared securely between the parties.

C. File compression: This is a process for reducing the size of data files for more efficient storage or transmission; it is not a method of encryption.

D. Data anonymization: This is a data processing technique aimed at protecting privacy by removing or obscuring personally identifiable information; it is not a type of encryption.

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

Rev. 5). U.S. Department of Commerce.

Section 2.1.2

"Asymmetric-key Cryptography

" Page 5: "Two different but mathematically related keys are used for a cryptographic process. In public-key cryptography

one key (the public key) is used for the cryptographic protection (e.g.

encryption or digital signature generation)

and the other key (the private key) is used for its reversal (e.g.

decryption or digital signature verification)." This directly supports the correct answer.

Section 2.1.1

"Symmetric-key Cryptography

" Page 5: "The same key is used for both the cryptographic protection and its reversal." This supports why option A is incorrect.

2. Rivest

R. L. (2017). Lecture 7: Public Key Cryptography. MIT OpenCourseWare

6.857 Computer and Network Security.

Page 1: "Public-key (asymmetric) cryptography uses two keys: a public key pk and a private key sk. The public key can be made public

while the private key is kept secret... If you encrypt a message m with a public key pk

you can decrypt the ciphertext c = E(pk

m) only with the corresponding private key sk." This confirms the use of two related keys for encryption and decryption.

3. Stallings

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

Chapter 9

Section 9.1

"Principles of Public-Key Cryptosystems

" Page 272: "The concept... involves the use of two keys: a public key

which may be known by anybody

and can be used to encrypt messages and verify signatures

and a private key

which is known only to the recipient

and is used to decrypt messages and create signatures." This clearly defines the two-key structure of asymmetrical encryption.