The term to google for more information about this would be Known plaintext attack.

Oh that makes sense. I assumed wrong that it was going to be about prisoners sending secret messages in their letters home, and the guards wanting to scramble those out.

	▲	01HNNWZ0MV43FF 8 days ago \| parent \| next [-]
		And the term for _that_ is steganography
	▲	onionisafruit 8 days ago \| parent \| prev [-]
		I clicked thinking it was about avoiding watermarks when exfiltrating data. I enjoyed the cryptography lesson I got instead.