Which scenario involves having access to both ciphertext and its corresponding plaintext?

Which scenario involves having access to both ciphertext and its corresponding plaintext?

• A. Known Plaintext Attack
• B. Chosen Plaintext Attack
• C. Ciphertext-Only Attack
• D. Brute Force Attack

Answer: (A)

Having access to both the ciphertext and its corresponding plaintext shows exactly how a specific piece of information is turned into the encoded form by the cipher. That pairing lets you see the relationship between plaintext and ciphertext, which is the hallmark of a known-plaintext attack. This kind of exposure can help you deduce the key or weaknesses in the algorithm by exploiting how the cipher maps known inputs to outputs. In contrast, if you only have ciphertexts, you’re dealing with a ciphertext-only scenario; if you can get ciphertexts for plaintexts you choose, that’s a different, chosen-plaintext situation; and trying every possible key without using any plaintext-ciphertext relationships is brute-force searching.

Having access to both the ciphertext and its corresponding plaintext shows exactly how a specific piece of information is turned into the encoded form by the cipher. That pairing lets you see the relationship between plaintext and ciphertext, which is the hallmark of a known-plaintext attack. This kind of exposure can help you deduce the key or weaknesses in the algorithm by exploiting how the cipher maps known inputs to outputs. In contrast, if you only have ciphertexts, you’re dealing with a ciphertext-only scenario; if you can get ciphertexts for plaintexts you choose, that’s a different, chosen-plaintext situation; and trying every possible key without using any plaintext-ciphertext relationships is brute-force searching.