Which of the following statements about basic encryption techniques is NOT true?

The statement regarding the key used in the Caesar cipher being made publicly available to allow the receiver to decrypt the message is considered inaccurate. In the context of the Caesar cipher, which is a substitution cipher where each letter in the plaintext is shifted a certain number of places down or up the alphabet, the key—typically the number of positions each letter is shifted—functions as a critical piece of information for both encryption and decryption.

In traditional cryptography, especially with symmetric encryption techniques like the Caesar cipher, maintaining the confidentiality of the key ensures that only authorized parties can decrypt the message. If the key were made publicly available, anyone could easily decrypt the ciphertext, defeating the purpose of using encryption to secure the information. Therefore, it is essential for optimal security that the key remains private between the sender and the receiver.

In contrast, the other statements regarding the one-time pad highlight the necessity of key confidentiality and randomness, which are fundamental principles in cryptographic practices. The one-time pad requires that its keys remain secret and that they are truly random, used only once to ensure perfect secrecy. Thus, understanding the nature of key management and its implications in different encryption methods is crucial in the study of cryptography.