A Level Computer Science OCR Practice Exam

What is the main characteristic of symmetric encryption?

1. Different keys for encryption and decryption

2. Same key for both encryption and decryption

3. Using public keys

4. No key required

The correct answer is: Same key for both encryption and decryption

Symmetric encryption is fundamentally defined by the use of the same key for both the encryption and decryption processes. This means that both parties involved in the communication must have access to the same secret key in order to encode and decode messages. The primary advantage of this method is its speed and efficiency, as symmetric algorithms generally require less computational power compared to asymmetric encryption methods. The requirement for both the sender and receiver to share and keep the key secure is crucial, as any unauthorized access to this key would allow an attacker to decrypt the messages. This characteristic distinguishes symmetric encryption from other encryption types, where different keys are used for each stage or public keys are involved. In contrast, options that suggest the use of different keys, public keys, or no key at all do not represent the foundational attribute of symmetric encryption.