Alice feels much more secure with her 64-bit keys and new algorithm (mutatis mutandis). But still, 10 days for an attack is not completely unrealistic if she has an important enough message to send. So, suppose Alice now decides on a 96-bit algorithm (otherwise DES-like in decryption time). By brute-force, Mallory and his TLA will need 2^40 hours to mount a brute-force attack on the message; in other words, Alice's message appears safe (against this particular attack) for 125 million years. Sounds pretty good, huh?