Page "Public-key cryptography" Paragraph 35

Of course, there is a possibility that someone could " pick " Bob's or Alice's lock.

Among symmetric key encryption algorithms, only the one-time pad can be proven to be secure against any adversary-no matter how much computing power is available.

However, there is no public-key scheme with this property, since all public-key schemes are susceptible to a " brute-force key search attack ".

Such attacks are impractical if the amount of computation needed to succeed-termed the " work factor " by Claude Shannon-is out of reach of all potential attackers.

In many cases, the work factor can be increased by simply choosing a longer key.

But other algorithms may have much lower work factors, making resistance to a brute-force attack irrelevant.

Some special and specific algorithms have been developed to aid in attacking some public key encryption algorithms-both RSA and ElGamal encryption have known attacks that are much faster than the brute-force approach.

These factors have changed dramatically in recent decades, both with the decreasing cost of computing power and with new mathematical discoveries.