Which of the following statement(s) is/are true regarding cryptography?…

Concept: Cryptography converts readable data (plaintext) into unreadable data (ciphertext) by applying an encryption algorithm together with a key. Kerckhoffs's principle (later restated as Shannon's Maxim) is the classical design rule for such systems: a cryptosystem must stay secure even when every detail of the algorithm is public knowledge — the ONLY thing that needs to remain secret is the key. This is why standard algorithms such as AES and RSA are published and openly scrutinised, while only the key is kept private.

Application to the statements:

• Statement I says ciphertext is the text obtained by running plaintext through an encryption algorithm — this is exactly the standard definition of ciphertext, so Statement I is true.

• Statement II claims that under Kerckhoffs's principle the algorithm itself must be private, with only the key secret — this inverts the principle, which actually requires the algorithm to be public and only the key confidential, so Statement II is false.

Cross-check (why the other options don't fit):

• Only II — would need Statement II to hold and Statement I to fail, but Statement I is the accepted definition of ciphertext, so this combination does not fit.

• Both I and II — would need Statement II to also hold, but Kerckhoffs's principle requires the opposite of what Statement II claims, so this combination does not fit.

• Neither I nor II — would need Statement I to fail too, but Statement I correctly describes how ciphertext is produced, so this combination does not fit.

Result: Since Statement I holds and Statement II does not, the correct choice is ‘Only I’.