A passive attack on a cryptosystem is one in which the cryptanalyst cannot interact with any of the parties involved, attempting to break the system solely based upon observed data (i.e. the ciphertext). This can also include known plaintext attacks where both the plaintext and its corresponding ciphertext are known.
While most classical ciphers are vulnerable to this form of attack, most modern ciphers are designed to prevent this type of attack above all others.
Read more about Passive Attack: Attributes, Further Reading
Famous quotes containing the words passive and/or attack:
“To make oneself an object, to make oneself passive, is a very different thing from being a passive object.”
—Simone De Beauvoir (1908–1986)
“The small perplexities of small minds eddy and boil about you. Confident from the experience that has led you out of these same dangers, you attack each problem as it appears, unafraid.”
—Alice Foote MacDougall (1867–1945)