What is ciphertext in a cryptographic system?

• A. The encrypted form of the plaintext
• B. The original plaintext
• C. A hash of the plaintext
• D. The private key used for decryption

Answer: (A)

Ciphertext is the encrypted form of data. When you apply an encryption algorithm to plaintext with a key, you transform readable information into ciphertext so it remains unreadable to anyone who doesn’t have the proper key. The point is to protect confidentiality—the original message can only be recovered by decrypting with the corresponding key. This is different from a hash, which is a one-way summary of data and not reversible to obtain the original message. It’s also not the private key itself, which is used for decrypting or signing, not the data produced by the encryption process. In practice, ciphertext is the scrambled output that, with the right key, becomes the original plaintext again.