Page 130 - CISSO_Prep_ Guide

By this process, Alice can send a confidential message to Bob
without needing to use an out-of-band method of secret key
exchange. Bob knows that the message came from Alice and
that the message is authentic and was not changed en route.

Cryptographic Attacks

Just as cryptography is valuable to protect data, a lot of effort
goes into breaking the cryptographic protection that
cryptography provides. There are numerous ways to attack
cryptographic implementations.

Attacking the key - The secret to breaking most cryptographic
implementations is to learn the key being used for the
encryption and decryption of the message. The key may be
discovered through a brute force attack - trying all possible keys,
but that is not practical for most systems today - the time and
resources it would take would be prohibitive.

Other attacks on the key can be made through linear and
differential analysis and known-plaintext attacks. With those
attacks, the cryptanalyst has copies of ciphertext and the
corresponding plaintext, and by comparing the texts, learns
some of the behaviors of the algorithm that can lead to the
discovery of the key.

The key may also be compromised in transit, guessed through
inadequate randomization, or stored in an insecure location.
The easiest and most vulnerable attack, however, has to be
social engineering. Bribery, idealism, coercion, romance, and
deception are all tools used by social engineers to convince
people to disclose cryptographic secrets.