Cryptography: Key Concepts and Types

Questions and Answers

What type of key system does traditional private-key cryptography utilize?

Two keys: one public and one private

Multiple keys for different users

One shared key between sender and receiver (correct)

Encrypted key exchanged over a secure channel

What is a key advantage of public-key cryptography over private-key cryptography?

It uses a single key for encryption and decryption.

It requires all users to have the same private key.

It is symmetric and provides equal security for both parties.

It simplifies key distribution without a key distribution center. (correct)

What are the two types of keys involved in public-key cryptography?

Secret and composite key

Shared and asymmetric key

Private and encrypted key

Private and public key (correct)

Which of the following best describes the asymmetry in public-key cryptography?

Encrypting messages requires a public key while decrypting requires a private key. Signup and view all the answers

What is a primary aim of public-key cryptography related to digital signatures?

To confirm that the message was sent by the claimed sender. Signup and view all the answers

What computational requirement must public-key algorithms satisfy?

It should be infeasible to determine the decryption key knowing only the encryption key. Signup and view all the answers

Which of the following is NOT a classified application of public-key cryptography?

Single-key systems for rapid message transmission Signup and view all the answers

What is necessary for a function to be considered a trapdoor one-way function in public-key cryptography?

It must be easy to compute in one direction but difficult to reverse without special knowledge. Signup and view all the answers

Study Notes

Private-Key Cryptography

Uses a single shared key for both sender and receiver, categorized as secret or symmetric key cryptography.
Disclosure of the private key compromises the security of communications.
Symmetry means both parties are equal, allowing issues such as forgery where the receiver can falsely claim a message was sent by the sender.

Public-Key Cryptography

Represents a significant advancement in the history of cryptography, emerging over 3000 years.
Utilizes two keys: a public key (accessible to anyone) for encryption and signature verification, and a private key (known only to the recipient) for decryption and message signing.
Asymmetric nature implies that parties within the communication are not equal; users cannot derive the private key from the public key.

Reasons for Public-Key Cryptography Development

Addresses key distribution issues, enabling secure communications without the need to trust a Key Distribution Center (KDC).
Facilitates digital signatures, providing a way to confirm the integrity and origin of a message.
Publicly introduced in 1976 by Whitfield Diffie and Martin Hellman at Stanford University, though concepts existed earlier in classified circles.

Applications of Public-Key Cryptography

Can be classified into three main uses:
- Encryption/Decryption: Provides message secrecy.
- Digital Signatures: Ensures authentication of the sender.
- Key Exchange: Secure sharing of session keys for symmetric encryption.
Some algorithms support multiple applications, while others are tailored for specific tasks.

Requirements of Public-Key Algorithms

Must ensure that obtaining the decryption key is computationally infeasible when only the encryption key and algorithm are known.
Confirm that encryption and decryption are computationally straightforward with the relevant keys.
In certain algorithms, either key can be used for encryption/decryption.
Requires a trapdoor one-way function, allowing easy computation in one direction while being difficult to reverse.

Description

This quiz explores the fundamental principles of private-key and public-key cryptography. Understand the significance of symmetric and asymmetric encryption methods, along with the implications of key management and security. Test your knowledge on the historical advancements and practical applications of these cryptographic techniques.